Praise be to Allaah.
A Muslim is permitted to marry a woman of the People of the Book, Jewish or Christian, so long as she is chaste and modest, as Allaah says (interpretation of the meaning): (Lawful for you in marriage) are chaste women from those who were given the Scripture (Jews and Christians) before your time [al-Maaidah 5:5]. But this is not recommended, especially for a Muslim who is living in a kaafir country under their laws and legislation.
It is not permissible for a Muslim woman under any circumstances to marry a non-believer (kaafir), whether he is of the People of the Book or otherwise, chaste or not, because Allaah says (interpretation of the meaning): they [believing women] are not lawful (wives) for the disbelievers nor are the disbelievers lawful (husbands) for them [al-Mumtahinah 60:10]
Todays Christians, so long as they claim to belong to, revere and follow Jesus (Eesaa), are among the People of the Book, and the rulings concerning the People of the Book that are recorded in the Quraan and Sunnah apply to them, but at the same time we regard them as kaafirs who have gone astray.
Even if a Muslim son marries a non-Muslim woman, his parents are still not permitted to disinherit him so long as he is still a Muslim and has not committed any offence which would put him beyond the pale of Islam. Anyone who does something that causes a Muslim to be deprived of his inheritance has transgressed the limits of Allaah, wronged himself and committed a grave major sin (kabeerah). Allaah rules as He wills and does as He wills.