Just remember how it is difficult sometimes to go over the hurdles of cultural differences IRL to have two people celebrate a wedding and live it well after that.
Now you have to think that:
Cultures really are different to the point that the concept of marriage doesn't apply at all
Breeding probably is impossible, so no children
Way of thinking, lifespan (longer or shorter) and all kind of subtle differences are in the way.
But like many of you, I think that with the proper atmosphere, if both parties get fun and no harm: Why not ?