I can see the logic in supposing that a "natural-born" polyamorist will tend to have less struggles with jealousy than a natural-born monogamist, as well as the logic in supposing that a practicing polyamorist will have more experience (than a practicing monogamist) in coping with what few jealousies he/she has.
I don't think I was ever meant to be a monogamist, but I was raised in a staunch monogamous Utah Mormon home, and I was definitely made to understand that one-man one-woman unions are the only unions sanctioned by God. I was in my church for life, and in that church, gay and poly marriage don't exist. So there is definitely no sharing, and every reason to plum freak out when one's spouse develops a new love interest. It's actually instant grounds for divorce.
But one day, long before my truly brain-twisting epiphanies wherein I said screw Republicans, and then, screw Libertarians because they're too Republican, and then, screw the church because its members and leaders aren't one iota more Christlike (let alone honest) than the mob ... long before those ugly days, back when I was still in denial that I could somehow fit in and still please Jesus: My wife, my best friend, and I were hiking in the mountains above my wife's hometown in Oregon.
During this hike, I had opportunity to reflect on some things. Like my best friend, who was always a little slow in some ways (but obsessively learned in things like Warhammer), who struggled socially and never could seem to be around women without great, awkward, uncomfortable, epic fail. It really struck me up in those mountains to observe him and my wife interacting -- comfortably, easily, joyfully, like lifelong friends. In my mind I thought, "It's like my wife is the only woman in the world who my friend could be with."
And then I was soberly asking myself, "So how about it cowboy? Would you be willing to share your wife with your best friend? assuming she was okay with it of course." I expected my next thought to be, "Yeah right, that's a leedle too weird." Instead, I bowled myself over by thinking, "That would be the coolest thing in the world. I've never been able to give my friend a decent gift -- not really. In this scenario, I'd be able to thank him properly for his friendship."
These thoughts were totally against church doctrine, and as such, represented something that could never happen. And I had no clue at that time that I was going to leave (or disobey) the church. Yet for a reason I can't explain, the idea *seemed* possible. Hell, everything seemed possible on that special day.
Never before in my life had I ever thought a polyamorous thought. So that day was the beginning of my long journey from monogamy to polyamory. But I suppose, given how easy that first step was, that I was always destined to end up in polyamorous circles. It was just a matter of time.
The first time I *ever* struggled with romantic jealousy was after I and my two companions had come together as a V. It was the first time any of us had practiced polyamory, and darn near the first time any of us had even heard the word "polyamory."
Well. Two (hetero) men and one (hetero) woman. Need I say more? There began to be situations when one man was off by himself, while the woman and the other man were off by theirselves, having sex or fun or laughing together or who knows what. This didn't bother me when the woman and I parted on good terms. But when we parted after an argument, all I could think about was how I was sitting alone in a state of rage, anguish, guilt, hopelessness, and bottomless lonesomeness, and she was off with the other man having a good time with him. It made me want to lash out at them, spew out sarcastic comments about what a great time I hoped they were having, "assuring" them that they needn't worry about the forgotten wreckage they had left on the side of the road.
Time and hard experience did gradually teach me that this jealousy I felt was actually a manifestation of things like separation anxiety, and the fact that I didn't feel like my needs were getting met. Over the years, as the lady of our V got better at meeting both men's needs, presto chango, I discovered that the jealous feelings (and all the indescribable angst that came with them) faded away and vanished.
Today I couldn't even tell you when's the last time I felt jealous. I suppose I might feel a microscopic twitch of jealousy now and again: not very often, not very painful, and not very significant. More like one of those weird thoughts that pops into your head out of nowhere and you think, "Where did that come from?"
Understand, then, that no matter how much harder it is for a monogamist to get past that jealousy than it is for a polyamorist: it can be done. It's all about figuring out what needs you need met, what special concessions, what little favors, what timely assurances, in order to soothe the owie feelings and make you feel like a whole person again. It takes a lot of time, patience, and communication. Did I mention it takes a lot of time? It won't happen overnight. But someday, maybe a year from now, you'll be able to look back and say, "Hey, I can see that I've made some progress."
One thing monogamists and polyamorists alike, as a whole, share and struggle with, is insecurity. The thought that, "Am I good enough? Do I deserve to be loved? Am I wanted just the way I am?" All of us have to work on those questions together.