I'm currently listening to some Orbital and I got to thinking that it's kind of neat when siblings get along creatively and make music. No special reason, but I thought it would be interesting to see just how many bands are made up of or include siblings. I'll start with a few I can think of.
Orbital - electronic duo consisting of Phil and Paul Hartnoll
The Knife - electro pop duo consisting of Karin Dreijer Andersson and Olof Dreijer
Stone Temple Pilots - rock band featuring brothers Dean and Robert DeLeo on guitar and bass
mewithoutYou - rock band featuring brothers Aaron and Michael Weiss on vocals and guitar
Oasis - annoying britpop band featuring brothers Liam and Noel Gallagher
...that's it off the top of my head.