It has happened twice to me....both FMF ..both times it was myself, mrs. blue, and a woman I had been fucking(not the same one both times tho) First time, Mrs. was in bed and I was playing with my friend when she said she doubted that the Mrs. had told me to go ahead and get laid (I already knew this one was bi) I took her by the hand to our bedroom and we asked the Mrs. if she minded...next thing I know is we are one the bed and both of us are sucking on the Mrs. tits when the F works her way down between her legs...INCREDIBLE SIGHT...she took turns alternating between sucking me and eating Mrs, then said she needed to get fucked....while I was stroking in and out, the MRs. speded things up by stroking my cock and balls...(dreamland in went on for awhile..reality is I came pretty quickly)
The second one was more or less set up by the Mrs... we were in our pool with a female friend that I had been fucking occasionally and all naked....the conversation got very graphic and Mrs said let's go inside..she lit candles, made sure the door was locked so nobody's kids could come in, and pulled out our toy box....the F and I sucked the Mrs. tits for awhile, and then we tied the F to the bed while the Mrs kept having me try different toys on her and the Friend....I got to fuck the wife for a few and then finish with the friend....
The chances of either situation happening again depend on who is around....And yes, what is good for me is good for her, I have encouraged MRs to think of what her own fantasies are...I do know one guy she almost fucked and we will probably set up either a MMF or depending on his wife or GF a MFMF very soon.