Hmmm, don't really have many exciting ones of these, sadly:
I know Mylo's (the dj/producer's) brother, he plays drums in a band where a good friend of mine from school is the bassist. Only met Mylo himself about twice though - he's alright.
Rustie apparently lives in the same neighbourhood as me but I've never seen or met him to my knowledge.
Non-musical ones: my dad's cousin is Ian Mcarthy, Labour MP who's been in a couple of minor-ish cabinet posts. He gave us a tour of Westminster once and we caught the last 5 minutes of PM's questions from the visitor's gallery.
Charles Kennedy was elected the president of the union at my old uni whilst I was working in the crappy canteen place there. He turned up really late for some function night, wanted food way after the dinner had been served, so me and a couple of the other night staff managed to cobble together some random stuff for him. Which to be fair he was perfectly grateful for. Couldn't tell for sure if he'd been drinking, but if I had to bet I'd say yes.
Edit: oh yeah, and as a kid I knew the same ex-Amebix member that Padraig mentioned a few pages back. This has been discussed on here before I think. He's fairly posh but very nice.