Source: Fatāwā Amunpuri by Shaykh Ghulam Mustafa Zaheer Amunpuri
What is the ruling on marrying the daughter of one's wife's foster brother while the wife is still in the marriage?
It is not permissible to marry the daughter of one’s wife’s foster brother while the wife is still in the marriage.
This girl is considered the foster niece (raḍāʿī bhatījī) of the wife.
Just as it is haram to combine a biological aunt and niece in one marriage,
it is equally haram to combine a foster aunt and her foster niece.
This is because any relationship made unlawful by blood (nasab) is also unlawful through fosterage (raḍāʿah).
Sayyidah ʿĀ’ishah رضي الله عنها reported:
إِنَّ الرَّضَاعَةَ تُحَرِّمُ مَا تُحَرِّمُ الْوِلَادَةُ
Ṣaḥīḥ al-Bukhārī: 2646, Ṣaḥīḥ Muslim: 1444
“Fosterage makes unlawful what blood ties make unlawful.”
① The wife’s foster niece (i.e., daughter of her foster brother) is maḥram through raḍāʿah.
② It is forbidden (ḥarām) to marry a woman and her foster niece at the same time.
③ The ruling of prohibition due to blood relation applies equally to foster relationships.
④ Thus, such a marriage is invalid and impermissible in Islam.
❖ Question:
What is the ruling on marrying the daughter of one's wife's foster brother while the wife is still in the marriage?
✿ Answer:
It is not permissible to marry the daughter of one’s wife’s foster brother while the wife is still in the marriage.
This girl is considered the foster niece (raḍāʿī bhatījī) of the wife.
Just as it is haram to combine a biological aunt and niece in one marriage,
it is equally haram to combine a foster aunt and her foster niece.
This is because any relationship made unlawful by blood (nasab) is also unlawful through fosterage (raḍāʿah).
Sayyidah ʿĀ’ishah رضي الله عنها reported:
إِنَّ الرَّضَاعَةَ تُحَرِّمُ مَا تُحَرِّمُ الْوِلَادَةُ
Ṣaḥīḥ al-Bukhārī: 2646, Ṣaḥīḥ Muslim: 1444“Fosterage makes unlawful what blood ties make unlawful.”
✔ Summary:
① The wife’s foster niece (i.e., daughter of her foster brother) is maḥram through raḍāʿah.
② It is forbidden (ḥarām) to marry a woman and her foster niece at the same time.
③ The ruling of prohibition due to blood relation applies equally to foster relationships.
④ Thus, such a marriage is invalid and impermissible in Islam.
