What is the ruling on a son marrying his sister's sister by suckling, who was nursed by his mother to the point of satiation?

Lactation establishes the same prohibitions as lineage, for the Prophet, peace and blessings be upon him, said: "What is prohibited by lineage is prohibited by lactation." Therefore, the girl who was breastfed by your mother is considered your sister by lactation alone, and not her other sisters. Accordingly, it is permissible for your son to marry the sister of your sister by lactation, unless another prohibitive factor is established between them. It is stipulated that the lactation which establishes prohibition must consist of five full feedings.