Sex and actors

I dunno how many of you are actors. I've done the ocassional short or a play, and I have a lot of filmmaking friends, so whenever they can't afford to pay a professional, I'll step right in.

There have been times I've been doing a more serious role, and in those situations (especially when I was younger and I took those aspirations seriously), it's best to immerse yourself in a character. Sometimes, you really have to get wrapped up in things- I'm sure other actors more professional than I know what I'm trying to elucidate.

Anyway, for anyone who's ever had a serious role, have you ever had a fling with an actor or actress playing alongside you as a family member? I remember I was dating a girl who auditioned with me for a play, and while I ended up being a lead male, she ended up playing my sister. This lead to some weird complications, and soon afterwards, we broke up. I dunno what it meant, but we were never the same when we were intimate afterwards- subconciously, all the crazy parts of sex vanished, and I really tried to pull back on the experimentation.

Anyway, anyone ever encounter something similar?