I'm planning to eat all of the chips and not save any for my brother.
That sounds mean, why wouldn't you save any for your brother?
I don't want him to stay fat and ugly
You should leave some food for your brother. It is up to him if he does not want to eat any.
He's such an annoying fat kid, ugh lets ignore him.
Your brother deserves to have food too, no matter his weight. You should leave some for him like a good brother.