Go for a walk with your parents and alternately run ahead/lag behind to annoy them.
When you've exasperated your parents, reluctantly agree to hold your brother's hand to 'keep an eye on each other.'
After you've grabbed his hand, reach over and take away the stick that he's holding with his other hand.
When he notices, hold the stick as far away as possible so he can't get it back.
Once brother's attention is elsewhere, hit him on the head with his own stick. Just because you can.
At the first sign of his protest, nonchalantly toss the stick over your shoulder so you don't look guilty and drop your brother's hand.
Distractedly puzzle over why your parents are laughing hysterically behind you.