I swear... This bitch is gonna ruin the family.
Anyway, I don't feel any chemistry between the little sister and older brother. So Author better not bulldoze through that route.
So the MC is just a fucking coward. You were bullied? Just get mad once and beat up your bullies a whole bunch. Traumatize them, hit them with chairs, tables, whatever near you at the time. If it works for me, it should work for you too.