Marriage between the son of a maternal aunt and the daughter of a woman who was breastfed by the mother

The questioner:
Honorable Shaykh, may Allah grant you success. He says: My mother breastfed my maternal aunt. Is it permissible for my maternal aunt’s son to marry my daughter?

The Shaykh:
No. What does he say?

The questioner:
My mother breastfed my maternal aunt.

The Shaykh:
She became a daughter of Allah.

The questioner:
So is it permissible for my maternal aunt’s son to marry my daughter?

The Shaykh:
No, because she became your sister. Since she became your sister, her daughters are forbidden to you. But your son, your son, has no relationship with her. Even if she is forbidden to you, she is not forbidden to him. Yes, unless there is a bond of breastfeeding connecting him to the one he wants to marry. If there is a bond of breastfeeding, she is not permissible for him; he is forbidden from her by breastfeeding, not by lineage. Yes.