Was sitting on a plane about six years ago (Paris to Montreal, so a long flight) once, this really charming guy was sitting next to me. We had pretty interesting conversation the whole way and sort of became friends. But he really corresponded to what you're describing, Bluetree: married, recently became the father of a young child, bored with his relationship. I can't remember the context, but I exploded with laughter at some point and told him outright he was just another textbook case of new-father-looking-for-something-"new"-outside-his-marriage. There are so many guys like that. I just told him that I refused to be a part of his mid-life crisis. We did stay in touch for a little while, and I will admit that the attention was welcome, but clearly he wanted to be more "friendly" than I was interested in.

I don't know if it's about the sex appeal, maybe. I suspect that it's a bit more than that.

I don't know what I'd do in your position, besides giving them a good shake and being as blunt as I was with that man. It's annoying because you probably enjoy these guys' company. But you probably don't want to get in the way of their relationship either... Even if you don't think that's what's going on, that's something to keep in mind. I know about the "I wish my wife cycled like you," and that would set off big big red flags for me.