Okay this might not count because I don’t have 100% confirmation from them, but this one family I knew I was extremely close with and I am fairly certain that their marriage was open on either both sides or just the wife. I am not entirely clear. I think they may have also been seeking a unicorn. Regardless, they were an interesting couple. Sometimes they fought, but they also had a level of directness and honesty towards each other that seemed like they really got to know each other in a serious way. So there was something interesting there going on, some kind of baring your real self and losing formal walls, but like I said I do not totally know the exact arrangement.