Back in my dating days I would date two girls at one time, but they did not have a relationship together. In truth a threeway relationship is a pot of trouble waiting to happen!Most people can't sustain that. I have not been in a married relationship like that.
In a sense you are a blended family but all parents are living together. In other cultures the wives have separate homes. And a man cannot marry unless he can provide equally for both. It isn't the harem idea I like, I like the relationship thing. To me being able to invest in two wives, maybe three, stops the need for infidelity, my emotional, physical and spiritual needs can all be met. It is taking a step away from sex and looking at holistic needs of individuals . The sister wives can have an intimacy they lack with the husband or a normal husband. They can have close loving bonds, almost as close as lovers can be. It isn't perfect but it does add depth.