Amended order unanimously affirmed without costs. Memorandum: Family Court did not abuse its discretion in modifying a prior custody order by awarding petitioner father custody of the parties' infant son. We give due deference to the factual findings of Family Court, which had the opportunity to observe the witnesses and assess their credibility, and its determination will not be disturbed where, as here, it has a sound and substantial basis in the record ( see, Eschbach v. Eschbach, 56 N.Y.2d 167, 173-174; Matter of De Losh v. De Losh, 235 A.D.2d 851, 853, lv denied 89 N.Y.2d 813). The contention of respondent that she was denied effective assistance of counsel lacks merit ( see generally, People v. Satterfield, 66 N.Y.2d 796, 798-800; People v. Baldi, 54 N.Y.2d 137, 147).