What is the ruling on my brother marrying a French Christian woman without a contract, with the marriage being announced among friends and family, except for our opposing mother, knowing that she previously bore a child out of wedlock, and she has expressed her unwillingness to return to that act while insisting on retaining her Christianity?

Islam permits marriage to a chaste woman from the People of the Book, with a legitimate contract that fulfills all conditions and pillars, even though these conditions are rarely met by women of the People of the Book in our current era. If your brother married her legitimately but did not formalize the contract, there is no sin upon him if the woman has abandoned fornication and committed to chastity. However, if the relationship was without a marriage contract from the outset, then this is forbidden. If, in addition, he had sexual relations with her, this constitutes adultery. Informing friends and family has no value; rather, it increases the sin because it is an open declaration of disobedience. The Prophet, peace and blessings be upon him, said: "All of my Ummah are pardoned except for those who commit sins openly."