It's Alive 3: Island of the Alive (1987)
They do something worse than kill. They multiply.
Third and final chapter of the "It's Alive" series. Mutant, murderous infants born across the country are sequestered on a remote island. Years later, the father of the original film's murderous tyke goes there to see how his son and the others are doing. But he ends up becoming their protector when mankind decides to exterminate them. Meanwhile, the exiled kiddies have not been sitting around sucking their thumbs. They've been breeding...