They're definitely not actually twins, either. I think... I think Chara might be some sort of weird spirit thing, except solid for some reason? They keep talking about names.

[He frowns, looking away. More things to ask Frisk.]

I don't know, Mabel. I think they are sad and alone. But that doesn't make it okay that they're killing people. And I'm not sure how we can stop them for good.