We have seen same and also have friends who do same.. the problem is this ... it is "not swinging", its cheating. They need to work on their marriage together, get in or out and this includes professional help.. and YES I have been on both sides including 30 years of domestic issues dealing in person with all sorts of couples., singles etc. It only leads to bad things including one being killed even some taking out the innocent kids.. ask me how many domestic related homicides I worked in south Florida.. and you may be surprised.
I have good friends male and female who do same and asked them why they dont get into swinging and the excuses they give are all over the map.. sorry its still cheating and told them so and they agree.
Swinging is an open line of communication and both parties are aware of ones sexual requests, be it hotwife, 3sums, 4sums, cuckholding, etc... according to those who are professionals: What Is a Swinger Lifestyle? “Sometimes that includes other couples, other times it may involve other singles, but usually it's focused on the committed partners having a shared erotic experience of some sort,” adds Dr. Kate Balestrieri, licensed psychologist, certified sex therapist, and certified sex addiction therapist. This could range from foreplay and oral sex to an entire evening of unadulterated penetration.