Well, currently, it's like this
A, B, and C live together, and to the outside world, function as a triad.
D and E live in another place, but we do make visits to them.
A and D, and B and E, are couples, in addition to that.
We emphasise openness and honesty in the relationship, so that if someone is starting to feel left out, ignored, or unappreciated, we can address that and make sure their needs are being met. We engage in activities together, but also sometimes do our own thing, depending on individual tastes and needs.
As far as being open sexually, I'll only touch upon it briefly, but we have a few rules we follow for sex outside the relationship, and if any of us, for example, B, has any significant objection to one of us, such as A, playing with a certain guy, it's encouraged for B to speak to A about it, gently and calmly. From there, the two can get to the bottom of why B feels uncomfortable with it, and resolve it, either by setting B's mind at ease, or not hooking up. That's where I'm leaving that.
D is the patriarch of the family as a whole, and A (myself) is secondary patriarch, and the one with more authority in the functional triad.
This family is also a leather family, however, so the way ours functions is probably not at all like most other gay poly open relationships work. I hope this helped give you insight.
A mite dyslexic, please forgive any small errors.