All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
It is absolutely not permissible for a Christian man to marry a Muslim woman, but if a Muslim man marries a Christian woman, he does not inherit her and she does not inherit him. It is confirmed that the Prophet said: “A Muslim does not inherit a non-Muslim, and a non-Muslim does not inherit a Muslim.” [Al-Bukhari and Muslim].
The above Prophetic narration is evidence that there is no inheritance between a Muslim and a non-Muslim. If a Muslim man dies, his non-Muslim woman does not inherit him. Similarly, if she dies before him, he does not inherit her.
At the death of a Muslim who has two wives, one of whom is a Muslim and the other is a non-Muslim, whether a Christian or a Jew, then his non-Muslim wife does not inherit him and it is only his Muslim wife who inherits him. She gets one-eighth if her husband has a child –whether a male or a female, and she gets one-fourth if her husband does not have children to inherit him.
For more benefit, please refer to Fatwa 89594.
Allaah Knows best.