The father appeals. A party seeking modification of an existing court-ordered custody arrangement must "show the existence of such a change in circumstances that modification is required to ensure the continued best interests of the child" ( Matter of Connell–Charleus v. Charleus, 192 A.D.3d 890, 890, 140 N.Y.S.3d 752 [internal quotation marks omitted]; see Matter of Errante v. Murry, 172 A.D.3d 711, 712, 99 N.Y.S.3d 379 ). "[J]oint custody is encouraged primarily as a voluntary alternative for relatively stable, amicable parents behaving in mature civilized fashion" ( Braiman v. Braiman, 44 N.Y.2d 584, 589–590, 407 N.Y.S.2d 449, 378 N.E.2d 1019 ; see Matter of Connell–Charleus v. Charleus, 192 A.D.3d at 891, 140 N.Y.S.3d 752 ).

Where, as here, a party seeks modification of an existing court-ordered custody arrangement they must "show the existence of such a change in circumstances that modification is required to ensure the continued best interests of the child." (Matter of Connell-Charleus v Charleus, 192 A.D.3d 890, 890, 140 N.Y.S.3d 752 [2 Dept., 2021]). Such a change in circumstances warranting modification will exist "when the relationship between parents becomes so acrimonious that it precludes opportunity for joint decision-making, the Court is within its rights to exercise its discretion to award sole custody to one of the parties."

"'A party seeking modification of an existing custody arrangement must show the existence of such a change in circumstances that modification is required to ensure the continued best interests of the child'" (Matter of Connell-Charleus v Charleus, 192 A.D.3d 890, 890, quoting Matter of Sidorowicz v Sidorowicz, 101 A.D.3d 737, 738). "The Family Court is in the best position to evaluate the credibility of the witnesses and its determination should not be disturbed unless it lacks a sound and substantial basis in the record" (Matter of Gold v Khalifa, 223 A.D.3d 803, 804 [internal quotation marks omitted]; see Eschbach v Eschbach, 56 N.Y.2d 167, 173-174).

"'[J]oint custody is encouraged primarily as a voluntary alternative for relatively stable, amicable parents behaving in mature civilized fashion'" (Matter of Robinson v Mustakas, 214 A.D.3d 880, 880, quoting Braiman v Braiman, 44 N.Y.2d 584, 589-590). However, "joint custody is inappropriate where parents have evidenced an inability to cooperate on matters concerning the child" (Matter of Connell-Charleus v Charleus, 192 A.D.3d 890, 891). "'[E]vidence of a hostile relationship between the mother and the father indicating that joint decision-making is untenable is a change of circumstances'" (Matter of Gold v Khalifa, 223 A.D.3d 803, 804, quoting Matter of Pierce v Caputo, 214 A.D.3d 877, 878-879).

"'A party seeking modification of an existing custody arrangement must show the existence of such a change in circumstances that modification is required to ensure the continued best interests of the child'" (Matter of Connell-Charleus v Charleus, 192 A.D.3d 890, 890, quoting Matter of Sidorowicz v Sidorowicz, 101 A.D.3d 737, 738). "[J]oint custody is encouraged primarily as a voluntary alternative for relatively stable, amicable parents behaving in mature civilized fashion" (Matter of Robinson v Mustakas, 214 A.D.3d 880, 880 [internal quotation marks omitted]; see Matter of Shields v Shields, 192 A.D.3d 691). Accordingly, "[e]vidence of a hostile relationship between the mother and the father indicating that joint decision-making is untenable is a change of circumstances" (Matter of Pierce v Caputo, 214 A.D.3d 877, 878-879).

"[J]oint custody is encouraged primarily as a voluntary alternative for relatively stable, amicable parents behaving in mature civilized fashion" (Braiman v Braiman, 44 N.Y.2d 584, 589-590; see Matter of Gray v Tyson, 205 A.D.3d 720, 722). "A change from joint legal custody to sole custody by one parent is warranted where the parties' relationship is so acrimonious that it effectively precludes joint decision-making" (Matter of Schweizer v Jablesnik, 95 A.D.3d 1341, 1342 [internal quotation marks omitted]; see Matter of Connell-Charleus v Charleus, 192 A.D.3d 890, 891). Here, the record demonstrates that, based on the relationship between the parties, continued joint legal custody of the children was inappropriate (see Matter of Connell-Charleus v Charleus, 192 A.D.3d at 891; Paruchuri v Akil, 156 A.D.3d 712, 713).

Upon our review, contrary to the mother's contention, we find that the Family Court did not err in declining to award the parties joint custody of the child. Joint custody is encouraged "'as a voluntary alternative for relatively stable, amicable parents behaving in mature civilized fashion'" (Matter of Shields v Shields, 192 A.D.3d 691, 692, quoting Braiman v Braiman, 44 N.Y.2d 584, 589-590; see Matter of Connell-Charleus v Charleus, 192 A.D.3d 890, 891). However, joint custody is inappropriate where the parties are antagonistic toward each other, do not communicate at all, and have demonstrated an inability to cooperate on matters concerning the children (see Matter of Connell-Charleus v Charleus, 192 A.D.3d at 891; Matter of Shields v Shields, 192 A.D.3d at 692).

f the children are always ‘paramount’ and the ‘rights of their parents must, in the case of conflict, yield to that superior demand’ " ( S.L. v. J.R., 27 N.Y.3d at 563, 36 N.Y.S.3d 411, 56 N.E.3d 193, quoting Matter ofLincoln v. Lincoln, 24 N.Y.2d at 272, 299 N.Y.S.2d 842, 247 N.E.2d 659 ). "Inasmuch as a court's custody determination is dependent in large part upon its assessment of the witnesses' credibility and upon the character, temperament, and sincerity of the parents, the court's custody determination will not be disturbed if supported by a sound and substantial basis in the record" ( Matter ofTurcios v. Cordero, 173 A.D.3d 1048, 1049, 100 N.Y.S.3d 569 ). " ‘[J]oint custody is encouraged primarily as a voluntary alternative for relatively stable, amicable parents behaving in mature civilized fashion’ " (Matter ofShields v. Shields, 192 A.D.3d 691, 692, 139 N.Y.S.3d 853, quoting Braiman v. Braiman, 44 N.Y.2d 584, 589–590, 407 N.Y.S.2d 449, 378 N.E.2d 1019 ; see Matter ofConnell–Charleus v. Charleus, 192 A.D.3d 890, 891, 140 N.Y.S.3d 752 ). However, joint custody is inappropriate where the parties are antagonistic toward each other, do not communicate at all, and have demonstrated an inability to cooperate on matters concerning the children (see Matter ofConnell–Charleus v. Charleus, 192 A.D.3d at 891, 140 N.Y.S.3d 752 ; Matter ofShields v. Shields, 192 A.D.3d at 692, 139 N.Y.S.3d 853 ).

"Inasmuch as a court's custody determination is dependent in large part upon its assessment of the witnesses' credibility and upon the character, temperament, and sincerity of the parents, the court's custody determination will not be disturbed if supported by a sound and substantial basis in the record" (Matter of Turcios v Cordero, 173 A.D.3d 1048, 1049). "'[J]oint custody is encouraged primarily as a voluntary alternative for relatively stable, amicable parents behaving in mature civilized fashion'" (Matter of Shields v Shields, 192 A.D.3d 691, 692, quoting Braiman v Braiman, 44 N.Y.2d 584, 589-590; see Matter of Connell-Charleus v Charleus, 192 A.D.3d 890, 891). However, joint custody is inappropriate where the parties are antagonistic toward each other, do not communicate at all, and have demonstrated an inability to cooperate on matters concerning the children (see Matter of Connell-Charleus v Charleus, 192 A.D.3d at 891; Matter of Shields v Shields, 192 A.D.3d at 692).

"'A party seeking modification of an existing custody arrangement must show the existence of such a change in circumstances that modification is required to ensure the continued best interests of the child'" (Matter of Connell-Charleus v Charleus, 192 A.D.3d 890, 891, quoting Matter of Sidorowicz v Sidorowicz, 101 A.D.3d 737, 738). "The best interests of the child must be determined by a review of the totality of the circumstances" (Matter of Walker v Sterkowicz-Walker, 203 A.D.3d 1165, 1167; see Friederwitzer v Friederwitzer, 55 N.Y.2d 89, 95-96). "