What is the ruling on a brother committing adultery with a foreign girl in France, then her becoming pregnant out of wedlock, and then aborting the fetus? And what is the ruling on his marrying her after the birth of a child out of wedlock?

Your brother has committed grave transgressions: establishing an illicit relationship, engaging in adultery, and urging the woman to abort, which is a crime, and its prohibition intensifies after the soul is breathed into the fetus. Blood money (Diyya) is due for it after its formation. He must be advised and warned about Allah, encouraged to repent, and to sever his relationship with this woman. If he is attached to her, he should marry her after their repentance and after her womb has been cleared. A child born out of wedlock is attributed to its mother, and residing in lands of disbelief may be a cause for such temptations.