The Ruling on Marrying a Full Brother's Sister Through Fostering

Question :

I wish to marry the daughter of my paternal aunt, bearing in mind that my brother, who is one year older than I, was breast-fed by my paternal aunt more than once. But as for me, I was never breast-fed by my aunt and my aunt's daughter was never breast-fed by my mother. Is it permissible for me to marry my aunt's daughter, or have I become a brother to her?

Answer:

The answer to this question is derived from the saying of the Prophet:
"What is unlawful by reason of lineage is unlawful by reason of fostering."

This means that breast-feeding makes unlawful that which kinship makes unlawful, because lineage is kinship and I have a comment regarding this word which I would like to make soon, if Allah, Most High wills. In this Hadith there is evidence that it. is permissible for you to marry the daughter of your paternal aunt who breast-fed your brother, because there is no connection between you and her, so you are not her brother, since you were not breast-fed by her mother and she was not breast-fed by your mother, so she is not your sister. Prohibition only occurs for the one who is breast-fed and his descendants. I mean that breast-feeding only affects the one who is breast-fed and his descendants. As for his brothers and sisters and their ante- cedents the prohibition does not extend to them. The prohibi- tion extends from the side of the one who is breast-fed, to him and to his descendants, and from the side of the woman who breast-fed him, and from the side of those related by her milk. That is, the woman who breast-fed him will be a mother for him, and her mother will be a grandmother for him, and her father will be a grandfather for him, and her brothers will be maternal uncles for him, and her sisters will be maternal aunts for him.

Similarly, one who is the source of a woman's milk, that is her husband, her owner (if she is a slave) or one who has had sex with her in error, is likewise a father and his sons are brothers to the one who was breast-fed, and his brothers will be uncles and his sisters aunts.

We derived all of this from the saying of the Prophet
"What is unlawful by reason of lineage is unlawful by reason of fostering."

As for what I promised (to speak about) a short while ago regarding the word An-Nasah, it is that many of the common people only understand the word Al-Ansab (lineage) or the word Al-Arkam (close relatives) to mean the kin of the husband and the wife, so that a man will say: "These are my Ansab, or my Arham," because he has married from among them - and this is an error, both in terms of language and of the Islamic Law, because Al-Ansab are the kin from the father's side or the mother's side and Al-Arham are likewise the kin from the father's side or the mother's side. As for the kin of the spouse, they are known as Ashar (in-laws), not Ansab. Allah, Most High says:
"And it is He Who has created man from water, and has appointed for him kindred by blood, and kindred by marriage. And your Lord is Ever All-Powerful to do what He wills."

Allah has declared the relationship between mankind to be based upon lineage and marriage. And they are two categories, that is to say, each of them is similar to the other, not the same as it.

I wanted to draw attention to this, so that the people will understand what is intended by the Islamic legal terms and not fall into error regarding them.