Is there a way to keep my family from using up all the bandwidth while I'm online?

My loser brothers are always on warcraft and so whenever I want to go online everything loads extremely slow and its incredibly annoying. I can't put a pword on our internet to keep them out b/c they'll just ***** to my father who pays for it. But is there any program (preferably freeware) that could knock them off the internet for awhile? Or some how else free up more bandwidth?