Nikah with a Woman with Whom One’s Grandfather Had Intercourse Is Haram

Question

A man has a maternal grandfather by blood, who has two wives. This man first committed fornication with his maternal step-grandmother, and after that took her in marriage. Is it permissible for a grandson to marry his maternal step-grandmother?

Answer

Fornication is fornication in itself; but nikah with a woman with whom one’s grandfather has had intercourse (mawtu’at al-jadd) is also haram. Whether the grandfather is the paternal grandfather or the maternal grandfather, nikah with a woman with whom either of them has had intercourse is impermissible, according to the words of the Exalted: [ar]وَلَا تَنكِحُوا۟ مَا نَكَحَ…

Source: Fatawa Mahmudiyya

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