Someone entering Islam while married to women unlawful to marry

Q 1: Here in Sri Lanka some Kafirs (disbelievers) have accepted Islam, especially Buddhists, but they stay married according to their former religions. One might be married to his niece and they have children. In such a case, we cannot separate them. What should we do?

A: If both spouses accept Islam together, and they are married in a way that is impermissible in Islam, they must be separated at once, such as a couple who accepts Islam while the wife is her husband's niece. (Part No. 19; Page No. 18) In such a case, they must be forced to leave each other, as it is impermissible for a Muslim to marry his niece. This is according to Allah's Saying (Exalted be He): Forbidden to you (for marriage) are: your mothers until His saying, ...your sister’s daughters and similar cases. A man who accepts Islam while he is married to two sisters is asked to divorce one of them. This is according to what was narrated by Ahmad, Abu Dawud, Al-Tirmidhy and Al-Nasa'y, on the authority of Al-Dahhak ibn Fayruz, from his father that he said, When I embraced Islam, I was married to two sisters. The Prophet (peace be upon him) ordered me to divorce one of them. The wording of Al-Tirmidhy is choose either one of them that you wish. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.