My sister had a baby with a guy, put him on the birth certificate but they are not married. She wants to leave him because he is very much an unfit father. He will leave the baby in the crib for 4 hours with a dirty diaper til she gets home and he has a child with his ex-wife whom he never sees and if behind on child support. When she tell him she wants to break up he threatens to take the baby. Can he do that?