How do you feel about a threesome? 🙈

Abigail
Okay so, before I met my now boyfriend I had been in a very emotional abusive and stifling relationship. When I finally left, I felt SO FREE. I've always found other women attractive, and I started seeing one. We never even kissed and it ended because I was more interested in "experimenting" and she wanted a relationship. We stayed good friends, now, I can't even look at her like that. I do, however, regret not hooking up with a girl before meeting my boyfriend now. He knows all about my desires and really wants is to have a threesome. We've discussed that if we ever do, only I should hook up with the girl and he could watch. Only because I still don't know how I feel about him with another girl even if I am present. He said he's okay if he never even gets to touch he just wants to watch lol. Do you think it would ruin our relationship? Have you ever had one?