Is it permissible for the daughters of a nursing mother to marry the brothers of their mother's nursling grandson?

It is not permissible for the man who was suckled by your daughters' grandmother to marry them, because he has become their maternal uncle through suckling, and it is forbidden for them to marry those who are forbidden by lineage, based on the Almighty's saying: "and daughters of the brother and daughters of the sister." As for his brothers whom your daughters' grandmother did not suckle, there is no objection to them marrying your daughters.