Being the spoiled golden child while his brother was abused by their dad and ignored by their mom completely warped his mindset. He developed a huge superiority complex, viewing his own brother as an inferior being.
But the thing is, Cheol is highly intelligent, and he isn't. His fragile ego couldn't handle the fact that someone he considered trash was actually way smarter than him ┑( ̄Д  ̄)┍

Ok I feel I dropped the ball somewhere. I know lillbro disliked/hated cheol, but why..? Cause he’s gay?