Edxl:
From a technical point of view, a story like that is a real commitment to write, because you are handling at least four characters and three relationships -- at least if you want to show their bisexuality in action. (it is also possible to just state that the character is bisexual and mention their attractions, but I don't think that is what you were looking for?)
So then you need to come up with a set-up that makes all three relationships interesting, showing different sides of the main two characters. And develop all of that.
I've actually tried a set-up like this, but the story just became longer than I felt was interesting, so I abandoned it.
Great to see you bring so much wisdom here, Edxl. Recently, we have had a number of writers post multi-character stories and really flesh out all the characters pretty well (no pun intended, really!!) I’m thinking of bcain’s latest and others.
Invariably, though, you have to make some characters into shallow almost cartoonish types. I really am starting to think of this bisexual idea as a challenge.
Hooper, can you tell more about why you want such a story and what you would like to see in it? Why do both main characters end up with partners of the opposite sex? And how does this setup relate to feederism?