Is it permissible for a Muslim father who married a Christian woman and had Muslim and Christian children to bequeath all his money to his Muslim son, and is it permissible for him to bequeath one-third of his money to his Christian son?

A will for a Muslim heir is not permissible unless approved by the other heirs. Scholars have differed regarding a will for an apostate. The correct view according to the Hanbalis and Shafi'is is that a will for an apostate is valid, and this is the most accurate opinion. A will for a Christian son is permissible, but it is preferable that it be less than one-third (of the estate), unless there is a benefit in doing so, such as inclining his heart towards Islam. A Muslim man married to a woman of the People of the Book is advised to raise his children upon Islam.