Ordered that the order is affirmed insofar as appealed from, with costs.
The court's paramount concern in any custody dispute is whether, under the totality of the circumstances, a determination of custody is in the best interests of the child ( see Eschbach v Eschbach, 56 NY2d 167, 171; Matter of Roldan v Nieves, 76 AD3d 634; Matter of Lamarche v Jessie, 74 AD3d 1341; Matter of Nikolic v Ingrassia, 47 AD3d 819, 820). Where modification of an existing custody arrangement is at issue, there must be a showing of a change in circumstances such that modification of custody is necessary to ensure the continued best interests and welfare of the child ( see Eschbach v Eschbach, 56 NY2d at 171; Matter of Lamarche v Jessie, 74 AD3d at 1341; Matter of Quinones v Ibarrondo, 67 AD3d 686; Matter of Pignataro v Davis, 8 AD3d 487, 488). "Custody determinations turn in large part on assessments of the credibility, character, temperament, and sincerity of the parties, and where a full evidentiary hearing has been held on the child's best interests, the resultant findings will not be lightly set aside on appeal" ( Matter of Roldan v Nieves, 76 AD3d at 635; see Petek v Petek, 239 AD2d 327). The Family Court's determination should not be disturbed unless it lacks a sound and substantial basis in the record ( see Eschbach v Eschbach, 56 NY2d at 173-174; Salvatore v Salvatore, 68 AD3d 966; Matter of Berkham v Vessia, 63 AD3d 1155).
Here, contrary to the father's contention, the Family Court's finding that there was a change of circumstances such that the children's continued best interests and welfare would be served by an award of sole custody to the mother has a sound and substantial basis in the record.
The father's contention that the Family Court should have ordered a forensic examination is without merit ( see Dana-Sitzer v Sitzer, 48 AD3d 354; Matter of Salamone-Finchum v McDevitt, 28 AD3d 670, 671; Matter of Diaz v Santiago, 8 AD3d 562, 563). The father's remaining contentions are without merit.