my boyfriend has the same fantasy...apparently its quite common...i was actually really offended at first..i mean i was thinking how can this guy love me and want to share me? i still dont really understand it..but we've moved past it...basically I made it clear that I am just unwilling to sacrafice MY morals and My beliefs just for one night that may or may not be great..could be REALLY awkward and could ultimately ruin the relationship...I believe that if you're in a relationship thats serious then it should stay monogomous period..I dont want another man...you really really do not want to sacrafice yourself for something you don't feel comfortable with...just sit him down and talk to him calmly..tell him you respect that he has this fantasy and you'd be willing to do ANYTHING to assist with this fantasy(buy a dildo or a doll etc) EXCEPT bring another man into the bedroom...i dont see how it wouldnt cause problems...I would never want to risk making my man feel inadequate or jealous just for one fantasy night...and i would never want to jeopardize the relationship..and he can sit there and say over and over again that it wont but I personally think that if he ever did get this fantasy out of me..his opinions of me would completely change...anyway...if you don't feel right with it..then just discuss it with him..its not your fault this wasn't discussed before the marriage

anyone can have fantasies, i have fantascies, but it's somethings i would never do.
do give into this, be straight up with him, tell him that will never happen because it would be breaking your vows, its adultery.
he shouldn't told you about this in the beginning.
my ex (good guy) told me he was in a threesome. then he told me the guy gave him oral, then one day he said he gave a guy oral. i felt so uncomfortable, but i got over it. he was bi-sexual! that's different, we were not married, and if we were i would have a big problem with sharing him.
is your husband bi-sexual?
you also have to be careful with std's in that type of lifestyle.