I never understood this thinking, and it's far, FAR too cliche in manga.
"This guy gets more female attention than me, I should kill him." ??? It's not like they'd be more interested in the guy who killed him, so what's the point?
Too many complaints lol, I mean everyone is still reading this so just ride it out to the end (if it ever ends). Rather than want to kill him I think y'all just wanna be him.
"As the brother, it makes %100 sense to kill him after all the man is marrying your both of your sisters along with ten other girls and as someone with a dick, it is natural to be jealous if not hate a person with a harem, a person who doesn't even deserve a harem too but who cares, we are all here to see some boobies."
-Eonlars @Kayriel