I don't want to help my younger brother with his school project
Why don't you want to help your younger brother with his project?
He is a piece of shit; he didn't even let me borrow his math book after I lent him 20 dollars.
Siblings should want to help each other out. You only have each other in the world. You should do what you can to support one another.
Shut up, asshole.
That is not a nice thing to say. Not helping out family members when they are in need is seen as rude. Siblings should try and help out each other more.