Is it permissible for the questioner or his brothers to marry his paternal uncle's daughter, who was suckled by his mother, along with his younger brother, more than ten full sucklings? Is it permissible for him to marry her sisters? And is it permissible to dissolve an engagement if the Fatiha was recited without knowledge of the Sharia ruling?

Fosterage establishes prohibtion [of marriage] just as birth does. So, whoever is suckled by a woman five or more times becomes a son to her and to her husband, the owner of the milk. It becomes unlawful for him to marry the foster mother and her children. Consequently, if your paternal uncle's daughter was suckled by your mother or by your father's milk five or more satiating sucklings, then she is your foster sister, and it is unlawful for you to marry her. The marriage contract with her is null and void and must be annulled. As for her sisters, it is permissible to marry them if they were not suckled by your mother or by your father's milk, because the prohibition due to fosterage applies specifically to the nursed individual and not to their siblings.