One Fantastic Beasts theory I’ve seen going around is that Credence Barebone and Leta Lestrange are half-siblings. Apparently there’s a family tree from one of the trailers and it looks like they’re related? Just recently, the part of Leta’s mother was cast, and she was described as “Corvus Lestrange’s first wife”, so it’s definitely a possibility. I would like to know how a child from a British family of wizards ended up with a magic-hating group in America, but hey, it’s not impossible.
We don’t know a whole lot about the Fantastic Beasts-era Lestranges yet, but their descendants are pure evil. Queenie immediately recognizes the name when she hears it in Newt’s thoughts and mentions their reputation for dark magic. Leta, a former friend of Newt’s, has been described as “complicated” and “misunderstood”, but even she is probably a Grindelwald supporter and certainly a murky, morally ambiguous type. I think, if Credence comes from the Lestrange family, it’s safe to assume that Mary Lou was actually right about his mother being a “wicked woman”.
It’s strongly implied in Fantastic Beasts that Mary Lou knew Credence’s mother. Given the strict laws meant to keep magic hidden in America, it could very well be that Credence’s parents are the only actual wizards/witches she’s encountered. While of course it doesn’t in any way justify child abuse, it’s easy to understand how someone who had history with the Lestranges, but had never met a good witch or wizard, might have a low opinion of magic-users.
And what about Credence now? Would the Lestranges accept a family member who was raised by muggles? Somehow I doubt it. Would they, like Grindelwald, want to use him as a weapon? I suspect so, especially since Leta seems to be working for Grindelwald.
Would Credence want anything to do with a family that really is every horrible thing he was taught to see magic as? I’d like to think no, but then again, he seemed so desperate to belong and be accepted that, with the right manipulation, he might.
One of the fascinating things about Credence is that he’s at the same time one of the most pitiful and sympathetic Harry Potter characters, and one of the most dangerous. He’s a lonely child desperate for affection and fiercely protective of others, but at the same time, he’s so desperate and so full of pent-up anguish that he’s vulnerable to being manipulated by those with less sympathetic intentions. And, of course, at his worst, he’s literally an uncontrollable dark cloud of anger and despair, destroying everything it comes in contact with. It’s really almost impossible to predict what he’ll do in future movies, because being conflicted and easily misled is one of his defining traits.