Milk Kinship

1. If an infant drinks the milk of a woman other than his mother, then that woman becomes the milk-mother of this child.
2. The husband of the milk-mother becomes the milk-father of the child.
3. The offspring of the milk-mother become the milk-brothers and milk-sisters of the child.
4. Nikaah between the milk-brothers and sisters is haraam.
5. Just as blood ties make nikaah haraam, milk-ties also make nikaah haraam.
6. Thus, just as a person cannot get married to his mahaarim in blood ties, the same applies to milk-relations; they become haraam.

(Behshti Zewar)