[476]*476BLACKBURNE-RIGSBY, Associate Judge:
This case involves a high-conflict and prolonged child custody battle between parents, appellant Brian Downing and ap-pellee Charlotte Perry, over their two minor daughters, M.D. and E.D. The primary issue we address in this appeal is whether the trial court abused its discretion by concluding that a “substantial and material change in circumstances,” D.C.Code § 16 — 914(f)(1) (2012 RepL), warranted modification of the parties’ 2012 custody arrangement. The trial court’s child custody modification granted Perry’s request to remove Downing’s tie-breaking authority in instances where the parties have a dispute over day-to-day legal custody matters, and instead vest that authority in a neutral Family Treatment Coordinator (“FTC”). The undisputed evidence revealed that Downing had disallowed essentially all extracurricular activities for the girls, and has never accepted the FTC’s recommendation when it differed from his own position. On appeal, Downing principally contends that the trial court erred in modifying the custody arrangement because Perry failed to demonstrate a substantial and material change in circumstances to justify the modification. He also argues that the trial court’s order delegated Core issues of legal custody to the FTC.1
We conclude that there was a substantial and material change in circumstances supporting the modification of the custody agreement in this high-conflict case, and that the trial court’s order did not delegate core issues of legal custody to the FTC. To summarize, there was an unforeseen change in circumstances since the parties entered into the 2012 custody agreement. In particular, the evidence revealed that Downing was given tie-breaking authority so that the parties would communicate more effectively, and so that he would feel more comfortable in authorizing more extracurricular activities for M.D. and E.D. Yet, Downing continued to exhibit a patterned negative response2 to Perry’s parenting, which manifested itself in his consistent rejection of the FTC’s recommendations in favor of his original position each time the tie-breaking process was utilized. Consequently, the girls were enrolled in fewer extracurricular activities than before the 2012 agreement, and Downing prohibited them from participating in activities in which they had previously participated. Notably, the trial court determined from the evidence that Downing had used his tie-breaking authority to essentially effectuate “de facto legal custody” over the children. Given such evidence, the trial court did not abuse its discretion in concluding that Downing had utilized his tie-breaking authority in a manner that was “not workable and [ ] not in the best interest of the minor children, e.g., extracurricular activities mushrooming into multiple issues affecting the minor children’s best interest, including their mental and physical well-being.” Accordingly, we affirm the trial court’s order modifying the parties’ custody agreement.
I. Factual Background
This appeal is merely the latest chapter in a long-standing conflict between the parties over their children. The instant action arises from a June 1, 2012, custody agreement between the parties that was [477]*477incorporated, but not merged, into a June 20, 2012, consent order by the court (“2012 agreement”).
A. History of Conflict
Downing and Perry divorced in 2006, and have two minor daughters, M.D. born May 1, 2001, and E.D. born September 19, 2003. Upon their divorce, the parties entered into a settlement agreement which granted Perry primary physical custody and both parties joint legal custody of their two minor daughters. Yet about one year later, on August 3, 2007, Downing filed a motion for sole legal custody of the children, contending that Perry made unilateral decisions pertaining to legal custody matters and sought to sabotage Downing’s relationship with his daughters.3 The parties ultimately settled the matter by reaching a new custody agreement via a consent custody order issued on March 19, 2009 (“2009 order”). Under the 2009 order, Downing and Perry maintained joint legal custody of the children and approximately fifty-fifty residential custody. [Id. A-2, 3] This agreement called for the parties to work with a FTC, who “shall assist the parents with joint decision-making and in resolving conflicts when such joint-decision-making is not feasible or the parties cannot agree to a joint decision.” [Id. A-11] The FTC was authorized “to resolve the dispute by issuing a written recommendation, which shall be binding upon the parties unless and until it is set aside or modified by the Court.” 4
Approximately one year later, on June 14, 2010, Downing filed another motion seeking full custody of the children, making essentially the same accusations as before, namely, that Perry made unilateral decisions and sabotaged his relationship with the girls. Pending trial, however, the parties entered into the instant 2012 agreement. Under the terms of the 2012 agreement, “[t]he parties shall share joint legal custody of the children ... [and] [i]n the event that the parties are not in agreement regarding a legal custody decision which impacts the health, education, religion or general welfare, including extracurricular activities, of the children, the parties will consult with a FTC.” However, unlike the terms of the 2009 order, Downing — rather than the FTC — now had final tie-breaking authority to resolve any disagreement between the parties on legal custody issues. The agreement explicitly states that “[b]oth parties agree that the FTC will not be asked to make decisions or have any tie-breaking authority. The FTC will only make recommendations.”5
According to Jamie Desjardins, the former Guardian ad litem who helped broker the 2012 agreement, she recommended giving Downing tie-breaking authority over disputed legal custody decisions to lower conflict. Specifically, she “hoped” that it would “relax” Downing and “make him feel more comfortable authorizing things [i.e., activities] for the children.” It was Desjardins’s “hope that if [Downing] had ... tie-breaking authority that he would feel like it would be okay for the [478]*478children to do certain activities because he wouldn’t have to worry that [Perry] would be signing them up for -other activities .... ”
Downing claimed that initially following the 2012 agreement he felt “a great sense of relief,” and thought the parties would “never see the inside of a courtroom again.” Perry verified that Desjardin had recommended giving Downing tie-breaking authority, and that it would be “very risky” for Perry to go to court. Perry hoped that, with the advice of a neutral third party,' Downing “might be able to make decisions in the best interest of [the] children.” She also thought it was the best deal “under the circumstances,” and that a third party individual would now “truly see the dynamics that were going on and would hopefully help [them] address those and work through them and communicate more effectively.”
However, despite the 2012 agreement giving Downing tie-breaking authority, Downing once again filed for sole legal and primary physical custody of M.D. and E.D. on August 19, 2013. A multi-day eviden-tiary hearing on whether to modify the 2012 custody arrangement between the parties followed.
B. The Evidentiary Hearing and Downing’s Use of the Tie-Breaking Power6
At the evidentiary hearing, the chosen FTC, Dr. Charles David Missar,7 testified that he began working with the parties in late-2012 or early-2013. Dr. Missar opined that’ the ■ conflict between the parties stemmed from “a long history of mutual mistrust.” He testified that although “there are many areas of the girls’ participation [i.e., upbringing] ... that they actually do agree on” the process of making joint decisions “in a reasonable and logical and rational manner has become so contentious” that even areas of agreement between Downing and Perry are lost in the fighting. For example, in order to avoid an immediate negative reaction from Downing, Dr. Missar counseled Perry to “phrase her suggestions” to Downing “in different terms so as to avoid making it sound like ‘this is what I want’ or ‘this is my suggestion.’ ” However, Perry did not have the same instant negative response to Downing’s suggestions. In fact, Dr. Mis-sar could not recall a single instance in which Downing made a suggestion and Perry exhibited the same instinctive negative reaction. Notably, Dr. Missar also testified that, in his experience as an FTC and in his professional capacity working with numerous families, he has not seen a “high conflict situation” where “it has been effective or productive” for one of the parents to have tie-breaking authority. The trial court credited Dr. Missar testimony that “[i]n terms of the practical effects, given the circumstances between the parties [i.e., Downing and Perry],” there was not much difference between Downing’s current tie-breaking authority and an award of sole legal custody.
The record reflects three instances in which Downing’s patterned negative response towards Perry thwarted the FTC dispute process, and resulted in Downing exercising “de facto ” legal custody of the children. On all three occasions, Downing perfunctorily rejected the FTC’s recommendation in favor of his own original [479]*479position. First, he unilaterally prevented M.D. from receiving a HPV vaccine, even though Dr. Missar recommended that “unilateral decision-making [in this matter] [was] not appropriate.” In Dr. Missar’s opinion, “[t]his type of decision goes to the heart ... of necessary joint-parent decision-making.” Nevertheless, in a one-sentence “tie-breaking” decision, Downing declared that, “Right now, I do not consent to the HPV [v]accine, and it won’t be done unless I do consent.” Second, Downing also prevented the children from attending Camp Wright, even though the summer camp fell during Perry’s week with the children. Dr. Missar diplomatically recommended that the parties should focus on gauging the girls’ interest in the camp, and that, having resolved whether the camp fell during Perry’s or Downing’s week, he believed that “unilateral decisions about, activities on another’s parent’s week [was] not appropriate.” Yet again, Downing in one sentence and without explanation stated, “[M.D.] and [E.D.] will not attend Camp Wright this summer.”
The third example merits extended discussion — Downing’s refusal to let the girls attend Girl Scouts and another extracurricular activity, Girls on the Run (“GOTR”). M.D. and E.D. had previously participated in both Girl Scouts and GOTR. Downing testified that he believed “Girl Scouts [was] a great activity,” and that GOTR was likewise a “good activity” that was “girl-oriented.” However, following the 2012 agreement, Downing used his tie-breaking authority to prohibit the -girls from participating in either activity, even though Dr. Missar explicitly recommended that the girls continue to participate in Girl Scouts because they both seemed to enjoy it. Dr. Missar even implored Downing that “for the sake of the girls and their consistency of participation with peers,” he should “make efforts to get the girls to these activities (or at a minimum allow the other parent to do so).” Following Downing’s decision, Dr. Missar- spoke with M.D. and E.D. about their interest in Girl Scouts and both of them indicated that they “liked participating in Girl Scouts. They had friends who were in Girl Scouts. They like some of the activities in Girl’ Scouts.... [And] [b]oth expressed some upset ... about not participating in Girl Scouts on an .ongoing basis.” Likewise, Perry testified" that, when she informed E.D. that she could not attend GOTR that year, E.D. became '“distraught, very upset.”
Downing first, testified that he thought the girls would be overly scheduled if they participated in either activity, and that there would be “logistical challenges,” given that Downing and Perry were divorced. Yet, later, Downing clarified that Girl Scouts had only “one to two scheduled” events per month, and conceded that he did not know whether M.D. was actually signed up for any extracurricular activities at present, and that E.D. only had .weekly tutoring sessions. In fact, Perry.testified that M.D. was not signed up for any extracurricular activities, and Dr. Missar opined that the girls were involved in.a “below average” number of activities for children of their age. On cross-examination, Downing gave a different reason for disallowing these activities, explaining that.he did not approve any activities for the girls on Perry’s custodial time because Perry had started taking E.D. to a few Girl Scouts meetings without first “following the process,” i.e., the 2012 agreement, which required the consent of both parents. -It appears that Downing likewise prevented the girls from attending GOTR because Perry had reserved slots for both girls on GOTR without his prior consent. According to Downing, he “wasn’t going to agree to that kind of underhanded leveraging behavior.”
[480]*480Dr. Missar’s testimony bolstered the trial court’s subsequent conclusion that Downing’s decision to prohibit the girls from attending the extracurricular activities was premised more on his mistrust of Perry and his patterned negative response towards Perry’s suggestions. Specifically, Dr. Missar testified that Perry approached him for advice on how to present the possibility of having the girls participate in Girl Scouts and GOTR, since both girls have “longstanding friendships” with individuals in these activities, and that “she saw them as reasonable after-school activities that would be beneficial for the girls.” Dr. Missar counseled Perry to couch the suggestion as if it came from the girls because Downing “react[s] very strongly against things that [Perry] suggests] on her own initiative.”
C. Trial Court’s Decision
In a thorough and detailed seventy-four page order, the trial court denied Downing’s motion for sole legal and primary residential custody of the children. The trial court granted Perry’s request that Downing’s tie-breaking authority over legal custody disputes be removed and instead vested in the FTC. Perry made this request in her opposition to Downing’s motion for sole legal custody, which the court construed as a cross-motion request. The trial court concluded that Perry had demonstrated a “material change in circumstances because she had not anticipated [Downing’s] ... consistent rejection of each recommendation made by Dr. Missar regarding the minor children’s extracurricular activities.”
The trial court further observed that Downing abused his tie-breaking authority, especially as it relates to denying requests for M.D. and E.D. to participate in extracurricular activities. Specifically, the trial court found that Downing’s “desire for total control and veto power over the minor children, drove him to unreasonably reject activities that could enhance the minor children’s lives[,]” in reference to Girl Scouts and GOTR. The trial court also considered the “mosaic of the family dynamics” and found that Downing “has never utilized his tie-breaking authority to make a final decision that was not in keeping with [his] initial decision before receiving Dr. Missar’s recommendation.” The court admonished Downing for effecting de facto sole legal custody over the children, even though the 2012 agreement did not provide Downing with “unilateral authority to make legal custody decisions,” nor did it grant Downing “the right to make final decisions regarding the minor children’s general welfare when the FTC process ha[d] not been engaged by the parties.” Lastly, the court credited Dr. Missar’s expert opinion that “neither party should have tie-breaking authority in a high conflict case such as this one.”
Ultimately, the court concluded that the current framework was “not workable and [was] not in the best interest of the minor children,” (emphasis added), and that “[t]he parties’ long history of an inability to communicate to reach joint decisions on most matters concerning [the children’s] general well-being” required the court to vest “the tie-breaking authority in the [FTC] and remov[e] it from [Downing].”8 See generally Johnson v. United [481]*481States, 398 A.2d 354, 361 (D.C.1979). Accordingly, the trial court ordered that the FTC “shall have tie-breaking authority regarding legal custody matters on which the parties cannot reach an agreement,” thereby superseding the FTC provisions granting Downing that right in the 2012 agreement. This appeal followed.
II. Tie-Breaking Authority
This court “will only reverse a trial court’s order regarding child custody upon a finding of manifest abuse of discretion.” Jordan v. Jordan, 14 A.3d 1136, 1146 (D.C.2011) (citation and internal quotation marks omitted). Moreover, the trial court’s rulings “come to us with a presumption of correctness.” Hutchins v. Compton, 917 A.2d 680, 683 (D.C.2007) (citation and internal quotation marks omitted). The exercise of judicial discretion, however, must be grounded “upon correct legal principles and must rest on a firm factual foundation.” Wilkins v. Ferguson, 928 A.2d 655, 666-67 (D.C.2007) (quoting In re T.L., 859 A.2d 1087, 1090 (D.C.2004)). Accordingly, “[w]e review a trial court’s legal determinations de novo but apply a clearly erroneous standard to its findings of fact.” Jordan, supra, 14 A.3d at 1146.
On appeal, Downing argues that the trial court abused its discretion in modifying custody by taking away his tie-breaking authority and awarding it to the FTC. Downing makes two arguments in this regard. First, Downing argues that there was no material change in circumstances justifying the trial court’s decision to modify custody. Downing’s second claim, which we only briefly address, is that the court abdicated its responsibility to decide “core issues” of legal custody, and instead conferred those rights onto the FTC.
A. Change in Circumstances
We have explained that “the court can modify [custody arrangements] ... if it finds (1) that there has been a change in circumstances which was not foreseen at the time the agreement was entered, and (2) that the change is both substantial and material to the welfare and best interest of the children.” Foster-Gross v. Puente, 656 A.2d 733, 737 (D.C. 1995);9 see also D.C.Code § 16-914(0(1). [482]*482The burden of proof is on the party seeking the modification, and is by a preponderance of the evidence. See D.C.Code § 16-914(f)(2). On this record, we conclude that Perry satisfied her burden of proof by a preponderance of the evidence that a substantial and material change in circumstances warranted the trial court’s removal of Downing’s tie-breaking authority and instead vesting that power in the FTC. ,
1. Material Change in Circumstances
We must first determine whether there was an unforeseen material change in circumstances before deciding whether modification of the custody arrangement would be in the best interest of the' children. See Foster-Gross, supra, 656 A.2d at 737. It is well-documented that Downing and Perry had a fractious relationship that affected their ability to make legal custody decisions for their children.' Downing repeatedly sought full custody of the children, accusing Perry of sabotaging his relationship with the girls and unilaterally making decisions on their behalf, even though the parties had equal legal rights. In particular, the record reflects that Downing’s biggest concern and source of discord was Perry’s supposed circumvention of his consent in signing the children up for extracurricular activities. Consequently, in this context, the, former Guardian ad litem, Desjardins, explained, that the 2012 agreement, which gave'Downing tie-breaking and therefore final decision-making authority, was an attempt on her part to reduce conflict and “relax” Downing, so that he would “feel more comfortable-authorizing things [i.e., activities] for the children.” Downing corroborated this sentiment, claiming he initially felt “a great sense of relief.” Likewise, Perry testified that she expected that a neutral FTC would help her and Downing communicate better, thereby allowing Downing to “make decisions in the best interest of [the] children.”
The expectations of the parties in entering the 2012 agreement, i.e., the FTC process in which Downing had tie-breaking authority would improve communications and increase the children’s extracurricular activities, were clearly not met. Notably, while it is undisputed that the girls previously attended both GOTR and Girl Scouts, once Downing received tie-breaking authority, he suddenly disallowed both activities, which left the girls with — in Dr. Missar’s ’expert view — a “below average” number of activities. In fact, other than tutoring, it does not appear that the children were involved in any extracurricular activities at all. Downing precluded the girls from attending, despite Perry’s wish that they participate, and despite Dr. Mis-sar’s recommendation that they participate on the basis that such activities would ensure “their consistency of participation with peers,” and was thus in their best interests.10
[483]*483Downing’s refusal was unreasonable — he explained that he refused these activities, which he himself characterized as “great” or “good” activities, because Perry did not follow the “process” of asking for his consent first. . Downing’s reason for disallowing these activities was more about his issues with Perry and his patterned negative response to her suggestions, and does not promote the best interests of the children. Further, the. hope that the 2012 agreement would lead to better communication between Perry and Downing was also unrealized. Downing failed to ever use his tie-breaking authority in a manner inconsistent with his original position, and essentially acted as if he had de facto sole legal custody of the children.
The trial court found that Perry had established by a preponderance of the evidence that there had been a material change in circumstances because Perry “had not anticipated [Downing’s] undisputed, consistent, rejection of each recommendation made by Dr. Missar regarding the minor children’s extracurricular activities.” See also Wilson v. Craig, 987 A.2d 1160, 1164 (D.C.2010) (concluding that there was a material change in Circumstances where the trial court found that the parties had entered into the agreement expecting a reduction in hostilities, but that the conflict had instead continued and escalated). The record supports the trial court’s findings and conclusion, and we discern no error.
In Wilson v. Craig, we similarly concluded that the trial court did not- err in finding an unforeseen material change in circumstances justifying a modification in custody. In that case, the parties had entered into a custody arrangement hoping that it would moderate the child custody disagreements between the parents, improve the contentious relationship between the parents, and reduce hostility of the parents towards each other. Id. at 1164. In Wilson, we concluded that the trial court did not abuse its discretion in concluding that an unforeseen material change was established where the conflict, between the parties had “escalated” since the execution of the agreement. Id. Similarly, in this case, the trial court did not err in concluding that Perry could not have foreseen that Downing would use his tie-breaking authority to exercise defacto sole legal custody over the children by precluding Perry from exercising her equal rights as a co-parent and by blocking even more of the children’s extracurricular activities than before.
2. Best Interest of the Children
Further, the record reflects that' Downing’s rejection of the girls’ extracurricular activities had a material impact on the children’s well-being. In particular, Dr. Missar noted in his recommendation that the girls - should participate in Girl Scouts because it was important for the girls to have “consistency of participation with peers.” The trial court also observed that the lack of extracurricular activities plainly could have an adverse effect on the' minor children’s mental and physical well-being.
We are also mindful that this is a high-conflict child custody case, and' the fact that Downing has never utilized his. tie-breaking authority to .make a decision contrary to his initial position. Such a result is not in the best interests of the children as it is tantamount to giving Downing de facto sole legal custody over the children. See, e.g., Jordan, supra, 14 A.3d at 1159 (concluding that a parent’s right to raise her children must be reconciled with the other parent’s same interest, and with the principle that a biological parent’s rights must ultimately give way before the children’s best interest); Prost v. Greene, 652 A.2d 621, 627 (D.C.1995) (concluding that conduct by one parent that “interferes [484]*484with the fulfillment of [the] children’s need for the guidance and love of the [other parent] may have a serious effect on the welfare of the children ”) (emphasis added).11
The trial court analyzed whether tie-breaking authority should be taken away from Downing based on the “best interests of the child” statutory factors. See D.C.Code § 16 — 914(a)(3); supra note 9. In concluding that the best interest of the children favored removing Downing’s tie-breaking authority, the trial court focused on the fractious nature of the parents’ relationship and,, Downing’s abuse of his tie-breaking authority. In particular, Downing’s “unreasonable” decision to exclude the girls from Girl Scouts and GOTR, which the court found was based more on his need for control than him seeking to enhance the children’s lives, and Downing’s use of the tie-breaking power to make “unilateral” decisions regarding legal custody matters. See generally D.C.Code § 16 — 914(a)(3)(G) (“[T]he capacity of the parents to communicate and reach shared decision affecting the child’s welfare[J”). The court also considered Dr. Missar’s expert testimony that neither party should have tie-breaking authority in a high-conflict case such as this. See Wilson, supra, 987 A.2d at 1165 (stating that the judge’s findings were well-supported by expert testimony and by first-hand observation of the demeanor of the parties and witnesses). Thus, in the trial court’s view, the parties would benefit from continued joint legal and physical custody of the minor children, but with the FTC having tie-breaking authority regarding legal custody matters, “[g]iven [Downing’s] past rigid exercise of his tie-breaking authority” which the court found was premised more on Downing’s patterned negative response of Perry’s suggestions, rather than making decisions in the children’s best interest. See generally D.C.Code § 16-914(a)(3)(Q) (“[T]he benefit to the parents.”). Based on this record, we discern no abuse of discretion in the trial court’s determination that it was in the best interests of the [485]*485children to remove Downing’s tie-breaking authority and vesting it in a neutral FTC.
Downing counters that the trial court’s determination that he had failed to prove a change in circumstances for purposes of his motion for sole legal custody precluded the court from thereafter concluding that Perry, on the other hand, successfully proved a change in circumstances, supporting the court’s decision to divest Downing of his tie-breaking authority. Downing argues that the trial court had observed the minor children to be “happy, well-adjusted socially, and ... doing well in school.” We are unpersuaded by this argument. As the moving party for sole legal custody, it was Downing’s burden to prove that there was a material change in circumstances warranting giving him full legal custody of the children. See D.C.Code § 16 — 914(f)(2). He failed to do that. His failure does not thereafter preclude Perry from proving that Downing’s behavior subsequent to the 2012 agreement constituted a different material change in circumstances warranting the removal of his tie-breaking authority.
Here, the trial court concluded that Perry had indeed proved by a preponderance of the evidence that Downing’s tie-breaking authority was not in the children’s best interests because he had unreasonably used this authority to preclude his daughters from joining beneficial extracurricular activities to their mental and physical detriment. The record supports the trial court’s findings that Downing’s categorical rejection of all recommendations by the FTC after Downing was given tie-breaking authority constituted a material change in circumstances and not in the girls’ best interest.
B. Delegation of Authority
We next briefly address Downing’s claim that the trial court’s order erroneously delegated all final decision-making authority over legal custody matters, including the “core issues” of visitation and custody, to the FTC. We conclude that this argument is without merit.
In Jordan, we observed that, pursuant to Super. Ct. Dom. Rel. R. 53, the trial court is authorized “to delegate decision-making authority over day-to-day issues to [a] parenting coordinator [FTC].” 14 A.3d at 1156 (emphasis added). However, we clarified that the “court’s ability to delegate authority to a special master or parenting coordinator has limits.” Id. Specifically, “a trial court may not abdicate its responsibility to decide the core issues of custody and visitation[,Y because “[b]y statute, when custody of a child is disputed, the trial court must decide what type of custody arrangement is appropriate.” Id. (citing D.C.Code § 16-914(a)(l)(A)) (emphasis added). Thus, in Jordan, we approved the trial court’s order which made clear that the parenting coordinator may “make decisions resolving day-to-day conflicts between the parties that do not affect the court’s exclusive jurisdiction to determine fundamental issues of custody and visitation.” Id. (emphasis in original).
Here, the trial court’s order states the following:
FURTHER ORDERED, that the Family Treatment Coordinator shall have tie-breaking authority regarding legal custody matters on which the parties cannot reach an agreement; the 2012 Consent Custody Order is modified by deleting paragraphs 2.iv. and 2.v. and 2.vii and all other provisions of the Order shall remain in [e]ffect[.]
The paragraphs of the 2012 order that the trial court deleted were essentially those that limited the FTC’s authority to making a recommendation on a dispute for Down[486]*486ing’s review and approval.12 Further, the trial court explicitly stated that “all other provisions of the [2012 agreement] shall remain in effect.”
Paragraph 2,i. of the 2012 agreement, which remains in effect, clarifies that the FTC process will be utilized only where there is a dispute “regarding a legal custody decision which impacts the health, education, religion or general welfare, including extracurricular activities, of the childreni,]” i.e., day-to-day matters. In' other words, although the trial court’s order modified custody by vesting the tie-breaking authority in the FTC, the FTC’s decision-making powers are still expressly governed by the preserved portions of the 2012 agreement, which make clear that it is limited to disputes regarding day-to-day matters involving the children, and not the “core issues of custody and visitation.” Jordan, supra, 14 A.3d at 1156.13
III. Other Issues
Downing raises three additional issues, which we can address more summarily. First, Downing argues that, because Perry only filed an opposition to his motion seeking sole- legal custody, he was not on notice that she also sought removal of his tie-breaking authority. Consequently, he argues, the trial court’s decision to grant Perry’s request to remove his tie-breaking authority violated his due process rights. A related issue was raised by Downing’s trial counsel prior to the start of the-hearing in. which' he argued that Perry “simply opposed” Downing’s motion for custody, and therefore “should be bound by [her pleading].” We are unpersuaded by this argument. The court’s decision, while informed by the initial pleadings, was ultimately decided by looking to the evidence in the record. We conclude that Downing’s argument on appeal is similarly without merit. As we stated in Moore v. Moore, 391 A.2d 762, 768 (D.C.1978):
Whether parties have impliedly contested a matter i.e., whether parties recognize that an issue not stated by the pleadings entered the case ... is determined by searching the trial record for indications that the party contesting the amendment received actual notice of the injection of.the unpleaded matters, as well as an adequate opportunity to litigate such matters and- to cure any sur-prisé from their introduction.
[487]*487(Emphasis added) (Citations' omitted). Here, the record demonstrates that Downing was on actual notice of Perry’s request to remove his tie-breaking authority based on her proposed findings of fact and conclusions of law submitted to the court prior to the hearing. The first page of Perry’s proposed order, which was - available to both parties prior to the start of the hearing, made clear that Perry sought to revoke Downing’s tie-breaking authority by stating that “the [c]ourt modifies the current custody arrangement between [Downing] and [Perry] to eliminate [Downing’s] tie-breaking authority....” The fact that Downing’s trial attorney raised the issue before the trial court prior to the hearing only further proves that he was on notice, and that he had ample opportunity to litigate the matter during the hearing.
Second, Downing argues that the trial court abused its discretion by refusing to consider the. “overwhelming evidence” that favored him in rejecting his motion for sole legal custody. He points to former Guardian ad litem Desjardins’s lay testimony in which she recommended that Downing be awarded sole legal custody, and FTC Dr. Missar’s expert testimony in which he appeared to have placed more of the blame on Perry.14
While the “trial court may not arbitrarily disregard, disbelieve, or reject an expert’s uncontradicted' testimony ... once there is some basis in the record for the judge’s refusal to accept an expert’s conclusion, we will not [substitute] our judgment against that of the finder of fact who saw and heard the witness testify.” Prost, supra, 652 A.2d at 629 (citations, internal quotation marks, and brackets omitted). Relatedly, it is well-established that “[a]n appellate court will not redetermine the credibility of witnesses where, as here, the trial court had the opportunity to observe their demeanor and form a conclusion.” In re S.G., 581 A.2d 771, 775 (D.C.1990) (citation and internal quotation marks omitted).
Although admittedly there was some evidence that appeared to favor Downing, the trial court was well within its purview as the factfinder to discount or minimize Dr. Missar’s and Desjardin’s testimony favoring Downing based on ample contrary evidence in the record. Specifically, the trial court’s order concluded that Downing had failed to show a substantial and material change in circumstances warranting giving him sole legal custody of the children primarily because none of his accusations levied against Perry, i.e., that she endangered the children, withheld medical treatment and information, and alienated Downing from the children, were substantially borne out by the evidence, and were rather essentially attempts by Downing “to make a mountain out of a mole hill.” Further, in denying his motion, the trial court was also not blind to.Downing’s own behavior, which the trial court characterized as a “desire for total control and veto power over the children.” Notably, the trial court weighed against Downing’s motion his own failure to abide by the terms of the custody agreement, such as his failure to timely notify Perry regarding any medical issues that arise with the children. Given this evidence, along with the many character witnesses who testified in favor of Perry’s parenting and the trial court’s conclusion that some of Downing’s allegations were unreliable based on his own contradicted testimony, the trial court was [488]*488well within its authority to deny Downing’s motion for sole legal custody. Accordingly, we will not supplement our judgment for that of the trial court. Prost, supra, 652 A.2d at 629.
Third, Downing claims that the trial court erred in awarding Perry attorney’s fees and costs totaling $18,111.02. His main argument is that Perry was represented on a pro bono basis and her retainer stated that the firm would “absorb its [internal costs] ... and cover necessary [external costs] up to $2,500[,]” and therefore Perry was not entitled to fees and costs that she was not legally obligated to pay. This argument is without merit. Preliminarily, the 2012 custody agreement states that “[i]f either party is found to be in breach of this Agreement, the non-prevailing party will be responsible for the fees and expenses incurred by the other party relating to the breach.” The contract obligates Downing to pay any attorney’s fees incurred by Perry in defending her parental rights. See Assidon v. Abboushi, 16 A.3d 939, 942 (D.C.2011). As we recently stated in Saxon v. Zirkle, 97 A.3d 568, 576 (D.C.2014), “this court and others have held that attorney’s fees may be awarded even though representation was provided on a pro bono basis.” Consequently, the fact that Perry was represented on a pro bono basis did not preclude her from being awarded attorney’s fees and costs for the services that the firm had provided. See, e.g., Centennial Archaeology, Inc. v. AECOM, Inc., 688 F.3d 673, 679 (10th Cir.2012) (observing that many “courts construe the term attorney fees to mean, not the amount actually paid or owed by the party to its attorney, but the value of attorney services provided to the party’) .(emphasis in original).
IY. Conclusion
We affirm the trial court’s decisions in all respects. The trial court did not abuse its discretion by modifying the custody agreement by removing Downing’s tie-breaking authority and vesting it in the neutral FTC. Further, we see no error in the trial court’s decision denying Downing’s motion for sole legal custody, or in awarding Perry attorney’s fees and costs. Accordingly, the order is
Affirmed.
Opinion concurring in part and dissenting in part by Associate Judge GLICKMAN at pages 488-89.