Brother I have a question.
My mother’s cousin proposed my younger sister . We said yes to the proposal and later we came to know that my mother was breast fed once by the mother of cousin, when my mother was only 9 months old or so.
Is this proposal Halal in the light of Islam, please write us a FATWA in the light of Islam.
Also, advice us with the next possible step in regards to should we do her marriage with him or not.
الجواب وبالله التوفيق
As per the situation described in your question, Nikah between your cousin and your sister cannot take place as your mother and your cousin are considered brother and sister through the milk kinship (Raza‘i). You and your sister are considered your cousin’s nieces through that relationship. Since performing Nikah with a niece related through blood (i.e. bhanji) is impermissible similarly it is haram to perform Nikah with a niece related through milk kinship. It has been mentioned in a hadith of Rasulullah Sallallaho Alyhi Wasallam:
بحرم من الرضاع ما یحرم من النسب (مشکوۃ شریف بحوالہ فتاویٰ محمودی
واللہ اعلم بالصواب