What is the correct course of action regarding a man who proposed to me, and I discovered that he has a child born out of wedlock? Should I proceed with the marriage, and what is required of me and him, Islamically, concerning this child?

First: Whoever repents and becomes righteous, Allah forgives him. "The one who repents from sin is like one who has no sin." Therefore, one should not look at this man's past, but rather at his current state. If he is righteous, religious, and of good character, he would be a suitable husband for you after consulting your family and seeking guidance from Allah (istikharah), while being careful to verify his circumstances and character from the social environment in which he lives.

Second: A child born from adultery is not a legitimate son of the adulterer. Therefore, he is not obliged to raise him or provide for him, nor does he become a mahram to his daughters. This is the view of the majority of scholars. However, some scholars, such as Ibn Taymiyyah, held that if the adulterer acknowledges his son born from adultery and attributes him to himself, then his lineage is established, and the rulings related to lineage are affirmed for him, such as the obligation of providing for him, raising him, mahramiyyah, and other matters. Acting upon this view is strengthened if he is able to include the child's custody with him and raise him upon Islam.