My first reccomendation is to go to a teacher, principal, etc.
If you're in a school where the staff doesn't give a crap, force them to; The next time the anklebiter comes after you with a stick, take the stick in one hand and a handful of his hair in the other, drag him into the office, and tell them in plain terms that this little crap has been giving you trouble for some time now and you want it to stop. Bonus if the stick has your blood on it.
If his brother comes after you, knock him over, drag him to the office, and tell them this schmuck has assulted you.
Alternately, thump the midget until he goes away. He only thinks he can get away with this crap because no one's thumped him for doing it before. If his brother comes after you, go nucking futs. Make an example of what exactly happens to people that decide you would make a good punching bag. This route ensures that you will never have trouble again.