Is it permissible for my daughter to marry my sister’s son after I breastfed my sister’s son, and my sister breastfed my son?

The suckling of a brother or sister by a foreign woman does not affect the rest of his siblings. The prohibition (of marriage) extends only to the suckling child, who becomes a brother to the sons and daughters of the woman who suckled him. Therefore, his brother, who was not suckled by her, is permitted to marry the daughters of that woman.