From the Islamic Ripley’s Believe it or Not, Islam says if you have been suckled by the same wet nurse as your spouse, you cannot be married because you are Brother and Sister.
MADINAH: Islamic law prohibits marriage with one’s wet nurse (for men), her husband (for women), her biological children and any nonbiological children she breast-fed. All such individuals are described as the person’s “mahram.”
Since there is no official system of documenting the names and identities of children who have been breast-fed by a woman, some young men and women sometimes end up accidentally marrying someone suckled by their own wet nurse. This can cause difficulties when couples find out later in life. If they have children, then things can be an even bigger problem.
“We were married for seven years before we discovered we were brothers and sisters. My mother-in-law had breast-fed me,” said Hayat, a schoolteacher from Madinah. “We were lucky as we had no children,” she said, adding that she and her ex-husband only learned that she had been nursed by his mother when an old family friend visited her home.
“She was astonished to find we were married. She reminded my mother that when she had had puerperal fever after giving birth to me, my former mother-in-law breast-fed me and that my marriage to her son was thus forbidden,” she said.
The story of Umm Abdul Aziz is more tragic. She was married for 30 years and mothered nine children before discovering her husband was her foster brother. “It happened out of the blue. An elderly man came to my husband one day and told him that we had been suckled by the same woman. He even knew people who knew of this and could testify as witnesses. We were greatly shocked and deeply saddened,” she said.