On hating part...
for most part, it was caused by misunderstanding... I guess.
due to Soo-in's personality:
he was pretty much stone-faced kid compared to his bright big bro.
and by the society's "norm" people would like his brother better.
when Soo-in was still a kid, he followed his hyung's steps into learning music, no harmful intent whatsoever,
but when his result was much better compared to his brother,
musical authority began to take care of him more, and forgot about his bro,
then those whispers about him being an attention seeker came around.
next? he simply stopped doing music for "his brother's sake"... cementing those rumors.
And where did the jack-ass senior come to play in this drama?
Well, from those brief flashbacks, I believe they met in that music prep school, and he totally regarded Soo-in big bro as his oqn brother, his idol even.
And he watched it firsthand how Seong-woo's "place" was steadily getting replaced by Soo-in.
On taking the blame part...
nothing were on the clear so far.
perhaps those people just think it was a re-enactment of something similar, something that people had assumed that Soo-in had done in the past to his big bro.
On could not sing part.
It was caused by his guilt.
The main cause will be revealed in next three chapters [15-17] (I had read it on U site)
One time, his hyung finally croaked under the pressure and bad result, then lashed out on Soo-in for his achievements.
Coupled with the uncompromising pragmatic adults in their surroundings,
Soo-in just opted to stop/repress it all.
Oh, I should add, that...
several times, Soo-in had asked whether his bro was okay with the changing big bro was experiencing, but the latter just chose to keep his brotherly image.
So, it wasn't like Soo-in don't care, it just that he simply trusted his hyung.
then... yeah, you know it.
can someone else explain why people hate him and is blaming him for "killing" his brother and why he can't sing