Question:
A father has two wives. From the first wife he has a son. The second wife has a daughter from a previous husband. Are the son and that daughter mahram to each other?
Answer:
He (the questioner) says: A man has two wives. Through his first wife, he has a son. The second wife, before marrying him, had been married to another man and had a daughter from that previous husband. Now the question is: Are that son and this daughter considered mahram to each other? In common speech we might casually call them brother and sister because they are under one household, but in Islamic law do they come under the category of mahram?
To understand this properly, we should not go by social custom or everyday language. In religion, the standard for determining mahram is very clear. A mahram is someone whom a person is permanently forbidden to marry. Whoever is permanently prohibited for marriage becomes a mahram. Whoever is not permanently prohibited is not mahram.
Allahﷻ Himself has given the list of such prohibited relationships in the Qur’an, in Surah An-Nisa (Chapter 4), verse 23. In that verse, Allahﷻ mentions clearly who are forbidden in marriage.
They include:
- Your mothers (biological mothers).
- Your daughters.
- Your sisters — whether they are full sisters (same father and mother), paternal half-sisters (same father), or maternal half-sisters (same mother).
- Your paternal aunts (father’s sisters).
- Your maternal aunts (mother’s sisters).
- Your brother’s daughters (nieces).
- Your sister’s daughters (nieces).
- Your foster mothers — women who breastfed you within the prescribed age (usually within the first two years).
- Your foster sisters — girls who were breastfed by the same woman who breastfed you.
- Your mothers-in-law (your wife’s mother).
- Your stepdaughters — meaning the daughters of your wife, provided the marriage with the wife has been consummated. If you married a woman and consummated the marriage, then her daughter from a previous husband becomes permanently forbidden for you.
- Your daughters-in-law (the wives of your sons).
- And it is forbidden to have two sisters in marriage at the same time.
These are the categories clearly mentioned. Whoever falls under these permanent prohibitions is mahram. Outside of this list, no one automatically becomes mahram.
Now let us apply this to the case in the question.
The man has two wives. From the first wife, he has a biological son. That son is the father’s child. The second wife has a daughter from her previous husband. That daughter is not the biological child of this man. She was born to another father.
Now we are not asking about the relationship between the man and that daughter. That is a different issue. The question is about the relationship between the son (from the first wife) and the daughter (from the second wife’s previous marriage).
Between these two children:
- They do not share the same father.
- They do not share the same mother.
- There is no blood relationship between them.
- There is no foster (breastfeeding) relationship mentioned.
So, according to the religious criteria in Surah 4:23, they do not fall under any of the permanently prohibited categories. They are not siblings in the legal sense. Calling them “brother” and “sister” in casual speech does not make them mahram in Islamic law.
Since there is no permanent prohibition between them, marriage between them would be permissible in principle. And if marriage is permissible, that means they are not mahram to each other.
Therefore, the son from the first wife and the daughter from the second wife’s previous husband are not mahram to one another.
