What is the ruling on a man marrying his sister's daughter through breastfeeding?

The questioner : The questioner says: Honorable Shaykh, there is a woman who breastfed. Her honor, another honor, her honor. Honorable Shaykh, there is a woman who breastfed a girl, and when this girl grew up, a brother of the wet nurse from her mother’s side married her. What is the ruling on this marriage?

The Shaykh : We apply, my brothers, this question to the rule we mentioned. This man married a woman who is related to him through breastfeeding.

The questioner : She says: There is a woman who breastfed a girl, and when this girl grew up, a brother of the wet nurse from her mother’s side married her. What is the ruling on this marriage?

The Shaykh : Well, this woman breastfed this girl, so she becomes her mother. The brother of this wet nurse becomes her maternal uncle, even if he is her brother from her mother’s side. Based on this, this marriage is invalid because the man married his sister’s daughter, who is his maternal niece, and it is well known that a sister’s daughter and a brother’s daughter are forbidden by way of permanent prohibition. So we say to the questioner: Hurry, may Allah reward you with good, to contact these people and inform them that it is obligatory to separate the man from the woman he contracted to marry. As for the children, the mention of the children is the mention of the children. We do not know.
In any case, if he was blessed with children before knowing the truth, then these children are attributed to him by the Shari'ah. Yes, and that is because the intercourse here was based on a doubt and ignorance, so lineage is attached to it. Yes.