I have threesomes on a regular basis. My other two partners are my left hand and my right hand. Awkward, initially, but it passed after lots of practice.
Mhm it can really strengthen bonds to act out a shared fantasy together, such as threesomes etc. I know I loved my boyfriend more than ever when he took me to a swingers party for the first time hehe.
Also, threesomes can sometimes be disappointing for the third person, but more enjoyable if you are part of the couple. I'm sure the married couple had a blast with you!
It takes a special kind of person to have a threesome and make it work. It really isn`t for everyone, but I enjoyed mine more than I thought possible. I would do it again in a heartbeat...