At this point I think we all unanimously vote for the brother
I would agree if the brother wasn't a jerk too. He clearly knows how to treat his brother kindly even when he was younger although he was still somewhat a jerk then too. Yet he insists on treating his brother even more poorly now that he's older? At least the blondie has a somewhat valid reason for the way he treats the MC. The MC was definitively the source of his trauma regardless of intent or the lack thereof.
Im still upset about li wi ding dying due to butterfly effect damnn ╥﹏╥