Is having a crush on a boy haram?

If you have crush on someone it is not considered haram in Islam. But you should not do any act on your crush which contradicts the principles of Islam. Loving someone admiring someone is not at all haram.

Is it haram to get a crush?

HAVING A CRUSH IS NOT HARAM IN ISLAM. BECAUSE LOVE IS THE FEELING WHICH YOU CANT CONTROL AND IT IS BEAUTIFUL NOT IMPURE OR DIRTY.

Is it haram to have a crush on your brother?

If you have crush on someone it is not considered haram in Islam. But you should not do any act on your crush which contradicts the principles of Islam. Loving someone admiring someone is not at all haram.