Um. Yes. Me, for one.
I have! I kind of came out indirectly via facebook status, but I had sort of hinted at it before in person, and it eventually filtered through to them. It wen’t pretty well - it wasn’t really a big deal to them, as far as I could tell. And they’re totally cool with it, even helping me make travel plans and propoganda for Ace Pride marches, etc.
Although, my parents are unusually awesome, so my experience seems to have been better than most.