Absolutely I do. I think we are all hard-wired differently. And like being hardwired to have attraction to the same sex, there are certainly those who are hardwired to have more than one deeply romantic connection at a time.
But like homosexuality, you potentially face some pushback from other folks in your life - people who find it confusing or unthinkable. You would get the same comments that someone would say to a gay guy like “Oh he just hasn't found the right girl yet.”
I have never been in any kind of polyamorous set up and I can’t foresee my partner and I doing this. But I often wonder if it is one of those things that seem better in fantasy than they would in reality. Once I made a friend while he was in a polyamorous relationship and I asked him, “Is it easier because you have more people participating and doing the work? Or is it tougher because you have more people to satisfy?”
He took a deep breath and just sighed out a single, “Yes.” This simultaneously told me nothing and told me everything. In truth, almost all polyamory scenarios I have personally encountered were short lived. But I have also met a triad who all three had been together for 22 years! So, I think it absolutely can work.
When it comes to navigating this feeling with your current partner, I advise to tread lightly. The more abrupt you are about it, the more of a shock it will be to him. And the more of a shock, the more his defenses will go up and he will be resistant to any change.
If you want to transition your relationship to something more polyamory-like, take baby steps. You said he already doesn’t want to open up sexually, so maybe a good place to start would be to tell him you’d like to experiment with threeways. This might certainly be a struggle for him, but at least he will feel included on it.
When he is resistant to this too, then I always suggest couples counseling with a therapist who has an (unbiased) emphasis on sexuality. This is what my partner and I did when opening up and we could not have been more grateful for it. The outcome was not determined when we began the counseling, but it guided us to a decision in a way that was healthy and constructive for us both.
From there, as you get comfortable with that, you can test new waters to open things up further. If you try this, BE PATIENT!!!! This process could literally take years. If you love your partner, remember, it is not all about what you want. In order to get what you want, you have to first give them what they need.
Best of luck,
PS - Oh, shit! I forgot the part about support groups. So yes, there might not be any support groups out there. But as I say, “Community is a ‘do it yourself’ project.” What I mean is that, if you can’t find what you are looking for, then create it yourself. Create the group, find others who have this same hardwiring, and gather regularly. If you approach life passively, you will get nowhere. So be active.