the father seems to have (obvious) anger issues and an inferiority complex towards his older brother (the uncle), so when cheol brought it up, it reminded him. like he couldn’t bring it out on his brother, so he’s taking it on his oldest son. at lease this is what i gathered, but i might be wrong and obviously doesn’t excuse his disgusting behavior. he shouldn’t be a father
I think it's the resemblance of their "inferiority complex" they both have towards their older sibling. Cheol's dad used to get abused by his father because the older brother (Cheol's uncle) was smart,whitty and socially out going. Their dad saw success in Cheol's uncle and chided Cheol's dad for not being on equal footing with his brother. Now a generation later Cheol's dad is projecting that inferiority complex onto Cheol because he sees his older brother reflected in him and thinks that "favoring" his younger son is the right thing to do and might give him a leg up, because now his younger son is in "his shoes" (which is kinda like confirmation bias). Which is kinda fucked cause Cheol's dad relies on Cheol's uncle quite a bit it seems. Fuck that guy
Yes i agree, this is what ive taken from the story so far aswell. His father has major inferiority complex. When Cheol was younger he simply hated him because he was the oldest, but as Cheol grew he started resembling his brother (the uncle) more and more which led to more abuse. The younger brother is clearly inferior to Cheol so the father resonates with that, in addition the little brother is also a shit stirrier because he likely also feels inferior to Cheol. So basically all these men and the mother are bitches.

I really don’t understand how his uncle could’ve left his nephew in that house after seeing how he is treated, at first I didn’t know he knew it was to this extent but it’s honestly astonishing he didn’t step in earlier bc apparently he did know. Also it’s not quite clear why his dad flipped out when he said his brother is his spitting image? (Did his mom have a affair or something?) adoption seems weird bc why would he be pissed if they chose it themselves?