What's your stance on Polyfidelity and/or Group Marriage...?

Polyfidelity is a form of polyamorous group marriage where all members of the group agree to only have sexual relations within the group. This was practiced in a small commune in San Francisco in the late 1900s, actually. I’m just curious as to what opinions people have on this subject.

I had heard of a sort of “group marriage” contract that is available in certain European countries, but never actually got to hear the details of how it works.

If a man loves a woman… And loves another man… And the woman loves them both… Would it be wrong? I mean… When you really consider a marriage, it is meant to progress to family. So would there really be a problem with… A larger family?