I'm going to tell my brother to shut up because he always sings and it's awful.
You want him to stop altogether, I assume?
I would rather have him stop his habit by all means possible. After all, I'm paying for his college tuition
Instead of telling him to shut up, you could ask him nicely and mention his tuition. Being rude could cause him to fire back and potentially annoy you further.
I'm not scared of him, he should behave since I pay for all his expenses.
It's not about fear. I'm just saying you're asking him to stop something he enjoys, so doing it politely is better.