In favor of polyamory or not, "they are fictional characters" is not a valid argument for whether a thing makes sense. By that logic, anything should happen with any character because the characters' personalities and histories supposedly don't matter.
A more salient argument would be "all the tension over the years between Jean, Wolverine, and Cyclops was because they really wanted to have sex together, but each of them were too afraid to approach the others", though that's not in the comics either.