How did his brother die?

Alot of theories flying around about his mother killing him or the ml killing him. All we know rn is that he fell from a high building.

He fell by himself I forgot what chapter it was but they did show it was his decision

It was.? Thank God

Yeah but that bitch did it to frame Seo in he was in the room with him and he wanted to do a final act to ruin his life sigh