Earlier quoted context omitted.
It's harder legally: marriages at the moment end when one partner leaves or dies. A polyamorous marriage on the other hand would be more similar to the board of a corporation since it theoretically could be immortal through consistently replacing partners.
> A polyamorous marriage on the other hand would be more similar to the board of a corporation since it theoretically could be immortal through consistently replacing partners. I remember reading a SF story that had that sort of arrangement, but I can’t remember the name.
A lot of Heinlein's stuff had polyamory at least in the background, it not front and center.
More recently, The Expanse dealt with it.
Though, honestly, the other spouses all just felt like 2D cutouts of characters, existing solely to show the "open mindedness" of the main character.
I don't think I've ever seen a story that really dealt with polyamory with all the characters having agency. Though, granted, haven't gone out of my way to look for it.