Kiddushin 19 - Designation of a Hebrew Maidservant as a Wife
A man who has bought a Hebrew maidservant can designate her as his wife, without the need for Kiddushin money, but with her knowledge. Can he do this for his son who is a minor? Does the phrase "or to his son" mean that the son can be any age or that he has to be like his father, an adult?
Answer: while a nine-year old CAN acquire a wife in levirate marriage if his brother dies by having marital relations with her, designation of a maidservant as a wife is not possible until the son is an adult.