It's what I try to figure out :
They were fuck buddies : no way but Siwoon knows how to kiss hum suspicious
They were doing their homework : they aren't classmates
The other twing I think is Jiwook was trying to seduce Siwoon
I hope not
It'll totally explain everything, the brother looks like the kind of bastard who believes he deserves everything good, while his brother is left with barely anything to survive. BUT, it's ok because our dear, crazy, Si-woon only has eyes for Taemin(Siwon)(๑•ㅂ•)و✧
Why was si woo with sijook in chapter 2 tho, why was he there, in the house...?