Once you have had a threesome things cannot go back to the way they were. How would you feel if your partner wants someone else as well as you. To me, that is a form of cheating. it is just a method for guys to get fully sanctioned extra sex. 3somes do not work out in relationships. Who can help but wonder if the girl or guy your partner is doing at the same time is a better kisser or a better f***. You will wonder for a long time if your partner was more turned on by the 3rd person.