I was thinking about your post this morning.
During the 7 or so years I spent being happily solo, I was not open to romantic relationships. I wasn't interested and most of the time if I was with friends who are in relationships, I couldn't understand why they were willing to put up with the restrictions that those relationships placed upon their lives.
Anyway – there during those years the only time I ever had a yearning for a close, committed, romantic relationship was with a couple I am friends with. Watching them together makes me smile – they are so relaxed and loving with each other. Sometimes I'd have dinner with them and go home wishing that I could go out with each of them. I have a very different relationship with each of those people and am much closer to one than the other but both of them are attractive to me – but more than that – their dynamic is attractive.
Over the course of the years, they were the only time I felt tempted to possibly look for something other than the lifestyle I was enjoying so much. Sadly, it had to remain a fantasy – my friends are not attracted to women and so I enjoyed and continue to enjoy them from afar.