DECISION ORDER
ORDERED that the order is affirmed insofar as appealed from, without costs or disbursements.
The twin boys at the center of this custody dispute have lived with the maternal grandparents since their birth on May 10, 1993. In June 1995, the biological mother, who is mildly retarded, married the biological father, and in October 1995, she tried to regain custody of the twins but the maternal grandmother refused to give them up. The biological parents then commenced a proceeding in Family Court, seeking exclusive legal and physical custody, and the maternal grandparents commenced a separate proceeding seeking the same relief for themselves. After hearing testimony from the parties, the court-appointed psychiatrist, and several caseworkers, the Family Court awarded custody to the grandparents with extensive visitation to the parents.
The record reveals that both parents have cognitive limitations and are ill-equipped to care for the twins, who themselves have special needs based upon their own delayed development. Taken together, these factors provide an ample basis for the Family Court's conclusion that there are extraordinary circumstances requiring that the issue of custody be determined in accordance with the best interests of the children (see, Matter of Bennett v. Jeffreys, 40 N.Y.2d 543 ; Matter of Gambino v. Vargas, 209 A.D.2d 893 ). Moreover, we agree with the Family Court that it is in the best interests of the twins to remain with their grandparents and half-siblings, with whom they have lived their entire lives (see, Matter of Moore v. McClenos, 259 A.D.2d 752 [2d Dept., Mar. 29, 1999]; Matter of Karen D. v. Florence D., 210 A.D.2d 165 ). Inasmuch as the Family Court is in the best position to evaluate the testimony, character, temperament, and sincerity of the parties, its findings are entitled to great weight and should be set aside only if, unlike here, they lack a sound and substantial basis in the record (see, Matter of Louise E.S. v. W. Stephen S., 64 N.Y.2d 946 ;Matter of Klat v. Klat, 176 A.D.2d 922 ; Matter of Coyne v. Coyne, 150 A.D.2d 573 ).
SANTUCCI, J.P., JOY, FLORIO, and LUCIANO, JJ., concur.