Is it permissible for a son to marry his paternal uncle's daughter if the groom's paternal grandmother (his father's mother) breastfed him completely, knowing that she is also the bride's maternal grandmother (her father's mother)?

If the aforementioned man was breastfed by his grandmother five full, satisfying times, then it is not permissible for him to marry his paternal uncle's daughter, because she is considered his sister through rada'ah (milk-kinship), and a brother's daughter is a mahram (unmarriageable kin). However, if the breastfeeding was less than five full, satisfying times, then the prohibition is not established.