Use it as an excuse to spend time with your brother!
Tell him you suck. It'll make him feel like the better brother. So you're doing it for BOTH of you!
I wish I had a quieter house. I have a roommate who works nights so he sleeps until 4pm, then my other roommate comes home at 5pm. So I don't have much time to play loudly. Though, they really don't mind if I play the drums. But being so 'new' at the guitar, doing scales and such is embarassing :-P