A man has a brother through breastfeeding, and this brother’s wife breastfed a girl. Is it permissible for the brother to marry this girl, or is she considered his sister through breastfeeding, making him her uncle?

The questioner : I have a brother through breastfeeding who is married, and his name is Muhammad. My mother breastfed him. The wife of this Muhammad, who is my brother through breastfeeding, breastfed a girl. I married that girl whom my brother’s wife through breastfeeding had breastfed, but I doubt the validity of this marriage. If she is the daughter of my brother through breastfeeding, then he is also my brother, which would make me her uncle. Or is she not related to me at all, and is our marriage valid? Please inform us about this. May Allah reward you with good.

The Shaykh : The Prophet (peace and blessings be upon him) said: . This man who was breastfed by your mother becomes your brother through breastfeeding, provided the conditions of breastfeeding are met, namely that there were five breastfeedings or more within the first two years or before weaning. In that case, he is your brother. If he married a wife and she breastfed a girl while she was still his wife, then this girl is not permissible for you, because she is the daughter of your brother through breastfeeding, and she is like the daughter of your brother by blood. Therefore, you are her uncle, and she is not permissible for you. Consequently, the marriage is invalid by the consensus of the Muslims. You must separate from her. If Allah has decreed that you have children together, the children are attributed to you, and you are their father, because when you came to this woman whom you married, you did so believing she was your wife, and the criterion is your belief. Therefore, the children are her children and also your children. However, you must now, and from the moment you hear this, separate from her and consider the first marriage invalid, and that she is not your wife.

The questioner : Yes, may Allah bless you.