It has to do with the father wanting to pass everything down to the son, even though he didn't want that life. The other guy wants it and admires the father, but the father wants to give it to his actual son.
no i get that ive read all the chapters but he keeps on saying mc reminds him of his father with disdain about it. If it was just that he'd be mainly bitter towards him, but he wouldn't throw shit at the dad too I think. I think there's something else that happened between them as well. But that's just my guess.
Maybe the way the MC act, the MC is kind and doesn't like violence, it could be that the gangster brother didn't understand the father but wanted to, and the MC was more connected with the father then him. The gangster brother probably see them both as "weak" ╮(￣▽￣)╭
So I guess yakuza step brother is sleeping with her confirmed. He clearly only cares about her because she's rich and "a catch". He seems so insecure..
kinda sad this guy turned into such a prick honestly when he grew up with them. Wonder what went down between him and their father. He admired him yet he keeps on saying mc looks or acts like the dad like it's a bad thing, so he clearly holds a grudge against their father too.