Well, "join" was my word, not theirs. They said they were "looking for a third." Apparently the wife has wanted this for some time and the husband didn't approve at first, until she somehow "proved" to him that there would be no jealousy issues. I don't know... this is the second time they've messaged me, the first being when I had a slightly different Craigslist ad up a couple of months ago. I looked in another section of Craigslist and they've also posted an ad, seeking either a male or a female for their third. It's a bit confusing... the more I think about it, the more uneasy I become. Part of me is just curious to hear more about it from them.