Your brother who was breastfed by your wife: you are his father, and his wife is a mahram (a relative one may not marry) to you

Question: My paternal brother was breastfed by my wife with a complete breastfeeding of more than one year. Is it permissible for me to greet the wife of this brother?

Answer: In the name of Allah, and all praise is due to Allah: This brother becomes your brother, and your son through breastfeeding, when your wife breastfed him five times or more within the two-year period. He is your brother by blood and your son by breastfeeding, and his wife is a mahram (a relative one may not marry) to you because you are his father through breastfeeding. There is no blame on you for greeting the wife of your son, because you are a mahram (a relative one may not marry) to her.