Kiddushin 20 - Terms of Servitude
A father can sell his daughter as a Hebrew maidservant to his own father (the girl's grandfather). Although the grandfather can not marry his granddaughter, he can designate her to marry his son, the girl's uncle, which is allowed by the Torah.
A master, who strikes a Canaanite slave and deprives him of his tooth or eye, must set him free. In contrast, a Hebrew servant in this situation receives payment but not freedom.
If a servant has a wife or children when he begins his term of servitude, then his master may give him a Canaanite slave-woman as a mate.