My wife and SIL have been husband swapping for years... when ever either of us visits the other, they swap husband for a night or 2 to everyones delight.... especially mine.. lol
I've didcussed this on another thread on NON-FICTION before... where I'm not sure... probably , "OPEN-Share your wife", thread?
Below the SIL ,34D, & wife 34B, best of both worlds?!!