Human beings have innate tendencies to sexual jealousy. Sure, with work and care, those tendencies can be overcome; but most people don't do the work and put in the care. And occasionally you'll find people who just naturally lack those tendencies, but they're quite rare (I have met a fair number of folks who claim to lack those tendencies, and all but one or two proved, ultimately, to be kidding themselves). When attempted as a real relationship dynamic, with truly egalitarian openness, I doubt the success rate would be more than one or two percent.
One of the interesting things about Sister Wives is that the wives do experience jealousy, but their anger about it seems to be directed at the husband, and not at the other wives. The first three, who have lived together for 16 years, seem to have their issues pretty much worked out, but the introduction of a fourth wife brought up a lot of jealousy. When the husband was "courting" her, the first three resented the time he spent away from home. Third Wife seemed to have the most trouble. She got very upset when she learned that Fourth Wife and her husband had kissed when they got engaged. She said she hadn't kissed him until they were married, because she didn't think it was appropriate to kiss a married man unless you were married to him. She also got very upset when she learned that her husband had picked out Fourth Wife's wedding dress: "Like you cared what
I wore!"
First Wife is all for polygamy, entered into the marriage with the understanding that there would be more wives, and seems to have instigated at least two of the later marriages, but she had problems with jealousy, too. At one point, she said she wasn't even sure why she stayed in the marriage; then she said mostly for her child and for the family.
All of the wives seem to like the "sister wife" concept. The first three are close to each other and are making an effort to bring the fourth into their circle. Second Wife says she never wanted to be a stay-at-home mom, and is glad that it's what Third Wife always wanted. Third Wife takes over a lot of the cooking, cleaning, and nurturing of Second Wife's kids, freeing Second Wife to work long days without worrying about the kids.
Each wife has her own "house" (apartment) in the house, but they all consider the other wives' kids as their kids, too -- even though each child lives with her biological mother. They're sort of like a group of very close neighbors who work together and help each other out constantly, only they all have the same husband.
Third Wife even said she always knew she wanted to be the third wife. She didn't want to be the only wife, because she wanted sister wives from the beginning. She said she was never interested in single men. She didn't want to be the second wife, either, because she thought that was a bigger adjustment, that the second wife has to insert herself into a previously monogamous household, and she didn't want to deal with that. She wanted to be the third, and she is.
I get the impression that the wives are content in their relationships with each other; in some ways, the circle of wives seems as important, if not more so, than their marriages to the husband.
Obviously, they're trying to put the best face on things, but overall I don't see anything at all wrong with how they're living. And all four wives together still have fewer children than the Duggars.