I have been involved in "threeways" in more than one situation. Some were just events that happened, some were planned and in two cases, long term and very well orchestrated. Some worked. Some didn't. Some I would jump right back into. The roles, activities, boundaries and comfort levels as well as limits, must be defined. If the people involved aren't adult enough, open enough and secure enough to discuss the activities and limits, as well as any fantasies they are interested in exploring, it isn't going to work. Yes, it is almost a business-like negotiation.
