My brothers friends? ual references?

my brother is 15 and im 16, is friends seriously piss me off wether its at school or his football club, they are always making ual inuendos at my expense, (air shagging me, my ****) you get the picture, but my brother never does anything, the other day i walked down the corridor at school and happened to walk past his cl, i got a whole load of cat calls and whistling, and he just sat at the back not doing anything. is he embared of me?? and why wont he stand up for me? tell his friends to piss off or anything? i feel hurt.