I'm having a problem with my girl friend and little brother?

Well, my girlfriend and I's parents are out of town and enlisted in the Army and leaving in 5 days. And i'm extremely nervous about it and having some bad anxiety while I'm trying to sleep. So since our parents are gone my girl friend has been coming over and sleeping with me, and we've been having as well pretty much every night,butmy 11 year old brother is down the hall and hes the biggest tattle tale in the world. And my Girl friend moans a lot and Im really afraid he might hear us, how can i can get my girl friend to stop moaning when we're having ? haha thanks. :) we're both 18 by the way