J and I have been together for almost 4 years, now, and we've always been mono. I started talking about polyamory about 2 years ago(but I actually vaguely suggested it before, I just didn't know there was a term for it) and he reacted very negatively. The subject came back a couple of times since then, and we did some intensive talking and thinking about it in the last month or so and he thinks he might be poly, too! We fought a lot, cried a lot, have been confused and ended up reconsidering everything in our relationship, but finally, we agreed!
I didn't think he was there yet, but he started reading a bit on the forum here and he brought up the subject of rules, and it turns out he doesn't want any rules, but respect, honesty and that we always make sure that the kids come first(we have 2 of them), which is what I wanted too, I just didn't think he was ready to talk about that. So... I'm pretty happy right now