I HATE HATE HATE that I can understand why the brother is so angry!!! Ugh the parents in this story are the biggest villains.
True that but we all have choices, and he chose because he was miserable (also understandable) to do everything in his power to literally make another human beings life as miserable as he could (hell he even tried to make him kill himself) that's where I find it not understandable. He never asked to be adopted as a replacement. Jaewon let his misery and anger consume him to the point he got off on ruining another person in hopes of breaking them til there was nothing left, and in that all to real sense is where I feel he lost any right to be understood.
I hate to say it but I dont understand the brother and I don't really think he was written for us to empathize with him as an 'understandable villain'. He is possessive with attention, not wanting to share any space with Seo-In, but we also don't see that he has any real interest in his parents. He's never shown to want more time or attention from his family or friends. Nor does he seem to want to take Yeongwoon's attention for any reason other than to piss Seo-In off. Jaewon just seems to have an extremely bitter personality, which mightve been from being chronically ill, than anything else.
He’s terminally ill and they knew that he was essential on a timeline and spent most of his time in and out of the hospital. His dad showed him attention, but primarily cared more for his career while his mom was never the same since the loss of her other son. I don’t agree with anything that he has done, but I can understand why he’s an angry child. Brining in a “healthy” child that everyone thinks looks just like you to the point that he can unlock your smartphone with facial id??? The mom was very insensitive when choosing to adopt him.
I know we all hate the brother, but you have to admit that adopting a new child after one passed away and while the other one is terminally ill may not have conveyed the most positive messaging to the sickly child.