Ep 11 (warning spoilers)

I wrote a whole essay here and then the tab crashed and it all got deleted and now I can't be bothered typing it all over again, why does this always happen to me! xD.. anyway.
I agree with this part of dramabeans recap of this episode:

''there’s a long-running jealousy there in how easily In-ho makes friends and wins people over. Jung is just one of those people who doesn’t know how to be that open and approachable, and it’s likely been a thing he’s envied in In-ho for a long time. He literally has the one thing Jung can never buy with all the money in the world. Perhaps he saw a shift in his father’s attentions as a teenager, and that’s what started the rift between the two boys. And if it’s happening all over again with Seol, I can certainly see how frustrating it could be for Jung, who only ever sees In-ho coming in and receiving love from the people Jung loves most. Told a different way, In-ho could’ve been the evil stepbrother who takes everything that Jung loves.'' 
Also the the preview for Ep 12! Inho admits he likes Seol, I'm pretty sure he doesn't say that in the webtoon but it's a drama so I guess they had to change it..