Hat tip: Ari Kinsberg.
According to this article, if a woman breastfeeds anyone, even an adult, the two are considered family and the usual restrictions regarding separation of men and women don’t apply. According to Islamic law, that is.
My husband points out that this could cause problems if the two (or their relatives) actually want to marry at a later point.
The Shulchan Aruch, based on the Talmud, allows breastfeeding until age two in all cases, and up to age 4 (or 5, if the child is sick) as long as the child has not ceased nursing for 72 hours. I know a few observant women who have nursed children older than that, but never discussed it with them. According to an article in Kolech’s collection on women and halacha by Dr. Deena Zimmerman, the reason for the restriction is that adults are forbidden to breastfeed (although they may drink mother’s milk indirectly) and the halacha designates the age of four to delineate between the two. I don’t remember what is special about age four, but will try to contact Dr. Zimmerman.
Halacha clearly considers breastfeeding until age two as a minimum. I know someone who thinks that a rabbi should be consulted before weaning a younger child. Whether this halacha applies today, when weaning may not visibly harm the baby, is a matter of dispute. In any case, rabbis need to recognize the health and emotional benefits of breastfeeding for both mother and baby when ruling on the subject.