Well this makes everything much more clear through implication. And I'm starting to get an image of why Mu Xiaoen has such unhappy feelings associated with her little brother, since it seems very likely now that he's her bio brother, grew up with their bio parents, and likely suffered in the way she would have had her real parents not adopted her away from that family. This would also explain why he's clingy and desperate for affection to both her and her parents.
Dunno yet what sort of darkness exists in Xiaoyang's parents that led to this situation. They seem to have money, so it's unlikely to be severe poverty or something individually debilitating. There's a number of very dark turns the author could take in this arc but hopefully we focus more on Xiaoyang and Xiaoen reconciling instead of detailing his suffering too much. That kid feels like he needs it.
Similar-ish to a situation from A Joyful Life. One kid "gets out" against their will and receives what they suspect is a better life...the other, not so much; then there's all the complicated interpersonal feelings that come from that.
Yeah, I'm convinced Xiaoen and Xiaoyang are biological siblings. At first I thought may be Xiaoen was adopted because her parents died in an accident but her brother is 18, so that gives them a 9-year age gap. She was adopted at 2, so the parents are probably alive. And after reading that letter from this chapter, I think their biological parents are rich elitists who gave up their daughter for adoption because they wanted a son instead. Or what if one parent died and the other remarried into a rich elitist family? So many possibilities but the bottomline is, they all have some sort of trauma.
Anyway, I wish I can reach into my phone and give these kids a hug. I hope Xiaoen succeeds in her grand plan of developing Peach Town into an inclusive and healthy environment (disguised as her youth program) for everyone. So far, it's going great and I don't remember seeing any despicable bastard in town.