The Rulings Resulting from Breastfeeding

Question:
If a child was breastfed by my mother, and the child’s father married another woman and had a daughter from her, is it permissible for me to marry her?

Answer:
If a child was breastfed by your mother, and the breastfeeding was complete with five feedings, then this child becomes your brother. As for his father, if he married a woman and had a daughter from her, this daughter is not your sister. She is the daughter of a wife other than your mother. This child became your brother because he was breastfed by your mother, who is the wife of your father. As for the father of the child who is an outsider, he has no connection to this. The child who was breastfed by your mother along with you, from your mother, becomes your brother, and you become the paternal uncle of his daughters.
As for the father of the child, you and his children are strangers to each other. You may marry the daughter of this man, who is the sister of the breastfed child along with you. She is his sister, not your sister, but she is the daughter of the father of this breastfed child. As for him, he became your brother because he was breastfed by your mother, not because he is the son of so-and-so, but because he was breastfed by your mother. And all the children of the husband who is the source of the milk, if he is your father, are your brothers. If he is your mother’s husband, then his children who were born from another wife become your brothers through the father. As for the father of the child who was breastfed by you, he and his children are strangers.

Question: Therefore, is it permissible to marry her?

Answer : Yes, he is a stranger.