Is it permissible for the paternal half-brother of so-and-so to marry a girl who was suckled by the maternal half-brother of so-and-so's mother, and for the paternal half-sister of so-and-so to marry that girl's elder brother?

It is permissible for the foster brother to marry the daughter of the foster mother, and for the son of the foster mother to marry the sister of the foster brother. This is because the prohibition due to fosterage is specific to the fostered child and his children only, and does not extend to his siblings, fathers, mothers, paternal uncles, or maternal uncles. Similarly, it is permissible for the children of the foster mother and the children of her husband to marry the siblings of the fostered child.