Source: Fatāwā Amunpuri by Shaykh Ghulām Mustafa Zaheer Amunpuri
What is the ruling on marrying the daughter of a foster brother (raḍāʿī brother)?
Marriage to the daughter of a foster brother is not permissible.
Such a girl is considered one's foster niece, and the man is her foster paternal uncle (raḍāʿī chachā). Just as marriage between a biological uncle and his niece is forbidden, so too is marriage between a foster uncle and his foster niece.
﴿وَبَنَاتُ الْأَخِ﴾
“And [forbidden to you are] the daughters of your brothers.”
Surah al-Nisā’ (4): 23
This prohibition includes both biological and foster nieces, as the wording of the verse is general and applies to all forms of brotherhood—whether by blood (nasab) or by breastfeeding (raḍāʿah).
① A man's foster brother’s daughter is his foster niece.
② Such a relationship falls under the prohibited degrees of marriage.
③ Therefore, nikāḥ with a foster niece is ḥarām (forbidden and invalid) in Islam.
❖ Question:
What is the ruling on marrying the daughter of a foster brother (raḍāʿī brother)?
✿ Answer:
Marriage to the daughter of a foster brother is not permissible.
Such a girl is considered one's foster niece, and the man is her foster paternal uncle (raḍāʿī chachā). Just as marriage between a biological uncle and his niece is forbidden, so too is marriage between a foster uncle and his foster niece.
❀ Allah ﷻ says:
﴿وَبَنَاتُ الْأَخِ﴾
“And [forbidden to you are] the daughters of your brothers.”
Surah al-Nisā’ (4): 23This prohibition includes both biological and foster nieces, as the wording of the verse is general and applies to all forms of brotherhood—whether by blood (nasab) or by breastfeeding (raḍāʿah).
Conclusion:
① A man's foster brother’s daughter is his foster niece.
② Such a relationship falls under the prohibited degrees of marriage.
③ Therefore, nikāḥ with a foster niece is ḥarām (forbidden and invalid) in Islam.
