Chucky Pewterschmidt was a former son of Carter and Babs and brother of Lois, Carol, and Patrick. He was mentioned in a deleted scene from some season 3 episode. It might have been that one where Brian got a boner for Carter's pet dog Seabreeeze Pewterschmidt.
Chucky was a developmentally disabled child of Carter and Babs. Carter was sick of raising a retard and so he decided to have him put down. Lois was old enough to remember him at the time. To cover up his crime, Carter told Lois that Chucky fell through the ice, while ice skating.
Years later, Lois revealed that she knows what really happened to him as a way of persuading Carter to give Peter a chance.