Hadith.4458 - Ali ibn Ri'ab narrated from Zurara, who said: I asked Abu Ja'far Imam Muhammad ibn Ali Al-Baqir about a man who married a woman in Iraq, then traveled to Syria and married another woman, only to later discover that she was the sister of his wife in Iraq. Imam said: "He must separate from the one he married in Syria, and he cannot approach the one in Iraq until the waiting period ('iddah) of the one in Syria is completed." I asked: "What if he married a woman and then married her mother, not knowing that she was her mother?" Imam said: "Allah (swt) excuses his ignorance in this matter." Then Imam continued: "When he learns that she is the mother, he must not approach her, nor approach the daughter until the waiting period of the mother is completed. After the mother's waiting period ends, it becomes lawful for him to marry the daughter." I asked: "What if the mother bears a child?" Imam said: "The child is his, inherits from him, and is both his son and the brother of his wife."