I think it's important that you confide to your loved one before you tie the knot. It's unfair and completely selfish to spring this kind of thing on someone. The only exception to this is when you didn't know or had to figure out what you liked. Hopefully you can grow together, but remember that this is a game for two, and awful when one does not like to play.
Ah, but as we know, in fantasy there is always a happy ending. - Or beginning...
One for the cuckold fraternity...