I have a cousin who is an only child, from a well-off family. After graduating from college, she studied abroad, married an American, and had two mixed-race babies.

She and her husband often travel back and forth between China and abroad with their children. My sister's parents have an average relationship, and her aunt feels lonely and wants to help her sister take care of the kids. My sister refuses, worried that the older generation's parenting methods are not scientific.
The aunt is very upset, feeling depressed every day. My uncle, seeing this, feels sorry and they decide to adopt a child as a grandson. Since my sister is an only child and her nephew is abroad, they figure they’re not short on money anyway.
After a while, my uncle actually brought home a boy who was a few months old. The aunt really liked him and treated him like her own grandson, spoiling him in every way. My sister was very unhappy but didn’t interfere much.
A few years later, my parents and I were having dinner and talking about this. I said I couldn’t understand what my uncle and aunt were thinking. My mom scoffed: xx (the boy’s nickname) is actually his own child, xx (uncle’s name) is a illegitimate son outside.
I was surprised: Then why does the aunt treat him so well?
My mom: She doesn’t know. The whole family knows, xx (sister’s nickname) also knows, but they’re hiding it from her. Sigh, no one dares to tell her. Maybe she already knows, but over the years, she’s developed feelings for him.
I suddenly felt speechless and heartbroken.