What is the ruling when a man is married to two young sisters (Sagheeratain) and the older sister nurses the younger sister?
General Chapter
Al-Mughni
Book of Fosterage (Breastfeeding)
Primary text
If the older sister (al-Kabeera) nurses the younger sister, the older sister becomes permanently prohibited to the husband because she becomes categorized as one of his maternal kin (ummahat al-nisaa). The marriage contract for both young sisters is dissolved because they become sisters to each other while simultaneously being in his marriage contract, similar to if they were nursed simultaneously. No dower is due to the older sister because the impediment originated from her. He is entitled to reclaim half the dower paid for the two young sisters from her because she invalidated their contracts. He may then marry whomever he wishes of the two younger ones because the dissolution of their marriage was due to the joining prohibition (al-jam'a) and does not establish perpetual prohibition.
Supporting text
According to the alternative narration, the marriage contract of both young sisters is dissolved upon the older sister nursing the first. If she then nurses the second, her marriage is not dissolved because she is no longer joined in marriage with her sister. However, if consummation occurred with the older sister before the nursing, she is permanently prohibited, and both younger sisters become permanently prohibited as well, because they are step-daughters whose mother (the older sister) was consummated.