السلام عليكم ورحمة الله وبركاته A brother has a haram child (girl) with a sister and now wants to marry her after repenting. If they marry, does he become a mahram for his daughter? & The sisters parents are and were not Islamically married when they had her, can her “father” be her wali?

Ustadh AbdulAziz al-Haqqan

He married her mother. Of course he's her mahram, even from that perspective.