1,508. The Consequences of Consecrating Unspecified Offspring
Hilchos Ishus 9:7
Let’s say that a man has five sons, each of whom appoints him as their agent to consecrate a wife. The man tells a friend who has five daughters, “One of your daughters is consecrated to one of my sons.” If the girls’ father accepts the kiddushin, each of the five brothers must give each of the five girls a get. This is because each of them empowered their father to consecrate a wife for him. If one of the brothers dies, each of the women must receive a get from each of the four surviving brothers, plus each woman must perform chalitzah (the shoe-removal ceremony) with one of the brothers.
Hilchos Ishus 9:8
Let’s say that a man has two daughters. One of them is either a minor or a maiden, whom he is empowered to give in marriage, while the other one is a legal adult. Even if the adult daughter empowers her father to give her in marriage, if he consecrates one daughter without specifying which, the assumption is that it’s not the legal adult unless he specifies that his older daughter, who is a legal adult, appointed him as her agent in this matter. Therefore, when no such specification has been made, the younger daughter is consecrated and the older daughter is not.