I proposed to my maternal aunt’s daughter, but I was told that her brother had been breastfed by my mother. Does my maternal aunt’s daughter become my sister through breastfeeding?

Question:
He says: I am a young man who proposed to my maternal aunt’s daughter. After I proposed to her, it became clear to me from her mother and my mother that her older brother had been breastfed by my mother more than seven full feedings. I am approximately five years older than him. My question is, Honorable Shaykh: Is it permissible for me to marry her, who is younger than me and has not been breastfed by my mother, and I have not been breastfed by her mother? Or is she in the position of my sister through breastfeeding, and is it forbidden for me to marry her? May Allah reward you with good.

Answer:
In the name of Allah, the Most Gracious, the Most Merciful. Praise be to Allah, Lord of the worlds. May Allah send prayers and blessings upon our Prophet Muhammad, and upon his family and his Companions. To proceed: If the situation is as the questioner described, then breastfeeding has no effect on the sister of the woman he wishes to marry from her mother. It is permissible for him to marry her as long as she has not been breastfed by his mother, and he has not been breastfed by her mother. The ruling is specific to the two who were breastfed and does not extend to their brothers and sisters. So he may marry this woman. Yes.