“This is concerning my question before abu Ja’far (a.s.), about the case of a man who marries in Iraq a woman; then goes to al-Sham (Syria) and marries another there who is the sister of the one in Iraq. He (the Imam) said, ‘He must separate from the one in al-Sham and must not go close to the woman until waiting period of the woman in al-Sham is complete.’ I then asked, ‘What happens if one marries a woman then marries her mother in ignorance?’ He (the Imam) said, ‘Allah has exempted people in their ignorance.’ Then he (the Imam) said, ‘When he comes to know that she is her mother he must not go close to her as well as to her daughter until waiting period of the mother is complete and when waiting period of mother is complete marriage with daughter becomes lawful.’ I then asked, ‘What happens if the mother gives birth?’ He (the Imam) said, ‘He is his child and thus his son becomes brother of his wife.’”