Is it permissible to disinherit a son who marries a non-Muslim woman, and are Catholics and Protestants today considered among the People of the Book, and is the prohibition of a Muslim woman marrying a non-Muslim definitively confirmed?

It is permissible for a Muslim man to marry a chaste Kitābīyah (Jewish or Christian woman), but it is not recommended, especially in non-Muslim lands. It is not permissible for a Muslim woman to marry a non-Muslim man. Contemporary Christians are considered People of the Book as long as they attribute themselves to Christ and venerate him, and the rulings concerning the People of the Book apply to them. If a Muslim son marries a non-Muslim woman, his parents are not allowed to disinherit him as long as he remains a Muslim.