Order unanimously affirmed without costs. Memorandum: Petitioner appeals from an order of Family Court that set aside a custodial arrangement, established by agreement of the parties and incorporated in a court order. He contends that such arrangement "should be changed based only upon `"countervailing circumstances on consideration of the totality of circumstances"'" (Fox v. Fox, 177 A.D.2d 209, 210-211, quoting Friederwitzer v. Friederwitzer, 55 N.Y.2d 89, 95; see, Matter of Aylesworth v. Aylesworth, 207 A.D.2d 970). Although a preexisting custodial arrangement should be accorded great weight, Family Court was "in the most advantageous position to evaluate the testimony, character, and sincerity of the parties" (DeJesus v DeJesus, 208 A.D.2d 587, 588, citing Eschbach v. Eschbach, 56 N.Y.2d 167), and the court's determination should not be disturbed where, as here, it has a sound and substantial basis in the record (see, Matter of Gloria S. v. Richard B., 80 A.D.2d 72, 76).