Is it permissible to marry the daughter of a man who was breastfed by my father's wife?

Suckling establishes the same prohibitions that consanguinity establishes, for the Prophet, peace and blessings be upon him, said: "Suckling prohibits what consanguinity prohibits." So, whoever suckles from a woman becomes a child to her and to her husband, the owner of the milk. If the girl's father suckled from your father's first wife after her marriage to your father, then he is considered your brother through suckling, because he suckled from your father's milk, and her daughter is unlawful for you because she is the daughter of your brother through suckling. However, if the girl's father suckled from your father's wife before her marriage to your father, then it is permissible for you to marry her daughter, provided that no other suckling relationship is established between you. The suckling that spreads prohibition must, according to the preponderant opinion, consist of five full, satisfying sucklings.