Many.
But I spend time in Islamic countries, and I very nearly married (legally, diplomatic status) into a polygamous family.
Here in the states: I know a few christian plural families (most hide the same way that smokers in our area hide, or gay/lesbian families used to hide; to keep their kids and themselves from being shunned and attacked... I've only ever "met" them on accident. Usually via a playdate when my son was little, because we talked about all the different kinds of families / they caught on really quickly that I don't give a rip &/or am all for committed relationships regardless of the way that the adults want to structure them. AKA we became a "safe" place for the kids to play & not have to watch their wording & any mom could come and hang out or drop off/pick up), and A LOT of non-married multiparent families (whether they consider themselves to be poly or not is up for grabs), and even more "open marriages"... where the extra people are NOT part of the family.
My feeling is this: Love is precious... and should be protected and cherished... however you happen to find it.
In my experience plural marriage is JUST like 2 person marriages; aka you find the abusive ones, you find the perfect ones, and you find the majority of them which are made of people who love each other despite all their problems.