Ordered that the order is affirmed, with costs.
It is well settled that in cases where a change of custody is sought, the relief should be granted when, in the court's discretion, "the totality of the circumstances * * * warrants its doing so in the best interests of the child" (Friederwitzer v Friederwitzer, 55 N.Y.2d 89, 96). "Since any custody determination depends to a very great extent upon the hearing court's assessment of the credibility of the witnesses and of the character, temperament, and sincerity of the parties" (Alanna M. v. Duncan M., 204 A.D.2d 409; see, Matter of Irene O., 38 N.Y.2d 776), its findings "are generally accorded great respect * * * and will not be disturbed unless they lack a sound and substantial basis in the record" (Kuncman v. Kuncman, 188 A.D.2d 517, 518).
Here, the Family Court properly determined that granting the father sole custody would be in the child's best interests. Its determination had a sound and substantial basis in the record. The Family Court was in a unique position to observe the parties and their witnesses testify, and carefully reviewed all the relevant evidence in making its decision. Although the parties' own agreement provided for joint custody, both parties expressed their desire to rescind the agreement when they filed petitions for sole custody. Copertino, J.P., Pizzuto, Altman and Hart, JJ., concur.