The husband learned that the woman he married was his foster sister, and he did not separate from her!
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Question:
He says: Honorable Shaykh, may Allah grant you success. If the husband and wife, as well as their guardians, know that they are foster siblings after the consummation of the marriage, but they tried not to separate them, and they are still married, is that considered making the unlawful lawful?
Answer:
This is not permissible; it is forbidden for him. It is not permissible to continue while they know that neither is lawful for the other. Enjoyment is not permissible; it is forbidden. Yes.
He says: Honorable Shaykh, may Allah grant you success. If the husband and wife, as well as their guardians, know that they are foster siblings after the consummation of the marriage, but they tried not to separate them, and they are still married, is that considered making the unlawful lawful?
Answer:
This is not permissible; it is forbidden for him. It is not permissible to continue while they know that neither is lawful for the other. Enjoyment is not permissible; it is forbidden. Yes.
Source
قناة «العلامة الدكتور صالح الفوزان»، [2073 -2802] عَلِم الزَّوج أن المعقود عليها هي أخته من الرضاعة ولم يفارقها!! - الشيخ صالح الفوزان — youtube.com
The Arabic text is a machine transcription of the audio recording.