Seems to me that a lot of the poly people I know can be pagan. Some of them even living lives fairly similar to those who are pagan.
But other than my own partner being pagan, I've had very limited time around it and would never be a part of it myself.
I'd say forget about the pagan aspect of it and just treat them as people you love. It's always interesting to bring up the topic and you could even get some of them thinking on it a lot more themselves.
As you say, a lot, if not all of them, were brought up being told love is only between two people and blah blah blah... But when you're with a group of generally open-minded people, you can really make them question the why.
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