Honestly I don't think Astarion needs fixing, sure I'm not going to help him murder his own kind on my main playthrough, but I'm also no going to redeem him either, personally kin should look out for their kin, like for example a Tiefling PC even an evil playthrough would more likely side with Grove than the Goblin camp, not because it's the right thing but rather it's their own people, I feel like freeing Astarion siblings should be similar, like yeah, Astarion you can still be an evil prick but you also can't go around killing family, Astarion dude you can repurpose them as your servants as a true vampire, you can treat them better than Cazador and still kick puppies, lock them in furnace if that's more your thing, steal people's girls and hunt down an entire bloodline if you must, maybe even father some illegal bastard kids with 4 different women and hook up with an equally morally corrupt male cleric just for fun down the line.
