I can't STAND my brother?! No parents here either?!?

I'm 18.. Have my license. My brother is 16. He complains that I'm not spending the money I got given from mum for food (while parents are in Hawaii). Fact is I am .. I've been spending it on KFC and McDonalds in addition to Supermarket shopping like he wants but he still complains. So he pays me back by dominating all of downstairs. For instance, now he has the music in the kitchen on full blast and I need to go down there a lot for food etc... What should I do? Anybody else got similar problems?