Is it permissible for a young man to marry his paternal uncle's daughter if his paternal grandmother (his father's mother) breastfed him after her milk had stopped due to her separation from her husband (the young man's paternal grandfather)?

It is forbidden for your friend to marry this girl because she is his paternal aunt through fosterage due to the milk of the male (foster father). It does not matter that the suckling occurred years after the death of the girl's wet nurse's husband and the cessation of milk, because paternity through milk is established even after divorce or death. There is no difference whether the milk was due to pregnancy or not, or if it was induced by treatment or intercourse.