What is the ruling on a mother nursing her son and daughter, and on the wife's mother nursing my son and daughter?

There is no harm in your mother or your wife's mother suckling your children. However, the children descend to your status if your mother suckles them, and to their mother's status if her mother suckles them. Thus, they become siblings to everyone your mother suckled, so the male among them may not marry his paternal uncle's daughters or his paternal aunts, and the female may not marry her paternal uncle's son or her paternal aunt's son, whether by lineage or by suckling. Furthermore, just as their descent to their father's status entails certain consequences, so too does their descent to their mother's status, meaning they may not marry the children of their maternal uncles or their maternal aunts, whether by lineage or by suckling.