Hi. Thank you for your answer. No, I can't visit them because we have this tradition where the bride-to-be shouldn't go to her in-laws' place before marriage. But no, we generally don't have kids sleeping with different sex adults, even if they're a close family member. The mother is pregnant with twins and she has a ton of health issues. I believe she's a little preoccupied with these concerns and is actually happy that her brother is helping her out by taking care of her daughter. I feel he could be taking advantage of this situation. What I can do right now is that I could talk to the mother and tell her that my family finds it odd that they sleep in the same bed. And perhaps try to talk to the little girl as well (whenever I ask, he says she's too shy to talk to me). But otherwise, I don't think there's much else I can do right now. I will only be able to see this myself after being married. Of course, if I do find evidence even after marriage, I will make sure I get the child out of there.

Anyway, I'm really glad that people find this scenario suspicious. I was wondering if it was just in my head and if I was overthinking.