Unless he has been extremely lucky, the brother has already gone through years of teasing and bullying at school. His life outside wouldn't otherwise be that easy either, seeing how most of the world is designed for adults with average adult heights. People suffering from dwarfism face extra challenges in life. The parents of these siblings should have tried to make sure the sister doesn't add to the brother's troubles. I'm not necessarily blaming the sister directly since she's still a teenager and teenagers just do stupid shit naturally, without knowing any better.