Sibling competitions are nothing new. It appears like when they are little children always need to pick on each other, and most will head to elaborate lengths to accomplish that. The small gouges accumulate with time while the huge fights often make permanent impressions.
Simply look at what this girl did for instance. While they were sitting at a restaurant one day, she determined to have a little pleasure (at his expense, obviously). What began as an easy prank rapidly turned into something hilarious!
He went from furious to amused in a matter of seconds. Certainly, getting a straw wrapper is not great, but getting one lodged in your ear is amusing.