“This is concerning my question before Allah’s virtuous servant (a.s.), about the case of my mother who has breastfed a girl along with me. He (the Imam) said, ‘She is your sister of breastfeeding.’ I then asked if she is lawful for my brother from my mother’s side whom she has not breastfed with his milk, that is not from this pregnancy but from another pregnancy. He (the Imam) asked, ‘Is the ‘impregnating agent’ (husband) one?’ I replied, ‘Yes, she is my sister from my parents.’ He (the Imam) said, ‘Because of the milk of “impregnating agent” your father has become her father and your mother her mother.’”