That's how I feel too. Seriously, I want to find something redeeming about Jiwook, but the fact that his brother committed suicide and he supposedly survived and Jiwook responded by trying to make him even more miserable makes me think that his character is not redeemable. Unless we find out that Han Siwon was fucking evil or something. But as I go through the raws, I find the opposite to be true.
UGH, tell me about it, imminent blue ball explosion here. I'm checking all the official and inofficial sites for updates of this manhwa more frequently daily than my friggin work mail ... and now I'm into this whole hopeless Jiwook/Joohoon powerplay mess marginally hoping for a romantic outcome which is obviously not happening.
AND YOU REMINDED ME OF DEADLOCK GOD BLESS YOUR SOUL! I even forgot who BB was, let me reread this and get back to you with an opinion about him. So what does BB have in common with Jiwook? Mental instability? Narcissism?
I'm most def sure darkhole is older than you.

After reading the raws and analyzing each chapter. I can go ahead and assume that siwon's brother was put in a situation where he either chooses to save himself or his brother. And as you can see, the brother grew up getting more and more jealous of siwon. So, he chose to save himself. One thing I'm sure of is that he feels bad for doing that, and some of you might say that "if he feels bad then why is he acting like an asshole" but while analyzing I think that he chose to distance himself from his brother, thinking that he doesn't deserve to actually be nice or a brother to him.
This is my analysis but I can be wrong and he turns out to be just a complete asshole.