Yep. I had a few with a married couple who had experienced lots of threesomes and group sex. It was a great experience because they were both really understanding and patient with me because it was a new experience for me. Everyone was open to sharing with each other and there was no jealousy or drama because we were all very open with each other and with our limits.
It sounds great in my head. But I have a my reservations. Mostly because of a failed marriage that failed because of sexual issues. But I've always wanted to. if my partner and I could find someone we both felt comfortable with then it may be a possibility.