diabolic, calm down...HEAPS of cousins do random shit like that. even though i kinda reckon its a bit weird....but what really is wrong is that u have a freakin gf...how do u reckon she would like it if she found out bout it? i dont imagine it would help ur relationship much. u need to end it with one of them. but its ur decision as to who. try having sex with ur gf instead.
If it feels good, keep doing it. I once walked in on my two younger cousins ages 7 and 8 - one had his pants down and the other was on his knees. At first I was gonna interrupt them and find out why they were doing that - but then I figured I better wait - no need to deprive someone of their pleasure. Just make sure your family doesn't find out, otherwise you'll be permanently banned from your own house.
is it rude to ask if you live in the south of america?