Mom: Dominic big boys don't wear diapers.
Dominic: (cheerfully agreeing) Nope, they wear big boy underwear.
Mom: And they don't drink bottles.
Dominic: (again cheerful) They drink from cups!
Mom: Big boys sleep in their own beds, not with their sisters.
Dominic: (confidently) Actually, big boys do sleep with their sisters, the girls will be sad if they don't.