Is one who was only nursed considered a brother or sister, or are all sons and daughters of the paternal aunt considered siblings to the sons and daughters of the two wives, and is it permissible for the sons and daughters of the second wife to marry the sons and daughters of the paternal aunt who were not nursed?

"What is forbidden by lineage is also forbidden by breastfeeding. Thus, the suckling becomes a child to the wet nurse and her husband, the owner of the milk. The prohibition is specific to the suckling and not to their siblings.

Based on this, the sons and daughters of the paternal aunt who were breastfed by the paternal uncle's wife are considered siblings to all the paternal uncle's sons and daughters. As for those among them who were not breastfed, they are not mahrams to any of those individuals except to those who were breastfed by their mother. Therefore, marriage is permissible between them and those who were not breastfed by their mother.

For breastfeeding to establish prohibition, there must be five full and satisfying breastfeeds."