Will a man forgive his wife who apostatized from Islam then returned seeking guidance from him, knowing that she had previously betrayed the marital bond?

A woman who apostatizes from Islam has her marriage contract annulled by her apostasy. If she embraces Islam and her Islam is good, and she repents from fornication, and it is confirmed that her womb is clear, then your brother can marry her with a new contract and dowry. Guiding people is not in the hands of humans; rather, it is a grace from Allah. The role of a Muslim is to convey the message, not to compel people to embrace Islam.