I get it, everything adds up when I think about.. Why he was so obsessed and protective of him! They were twin brothers! But thats actually so messed up and heartbreaking :(
A plot twist? you missed to interpret his actions towards Yoseob. (thoo i thought Yoseob tried to kill himself) that is why he said "he is little different"
Oh man! Reading this, I was all tensed up.. i love this!