If Possibility's primary relationships were to fail there's no way I'd take the blame. They are all adults & can make their own decisions.
I MIGHT feel a sense of guilt for a few days, especially if he broke the news to me just after we last saw each other, but once I had a chance to sit down with myself & go through what I knew from my own personal observations I'd be ok with it. I don't know how well my friendship with the other partners would hold up since we don't have much in common other than our love for Possibility but who knows.
"Internally" I would fear the affects of Redpepper's desire/need to form other relationships. Internally I also would have a hard time accepting that I was indeed not the cause of thier relationship failing. With a past of hurting people such as my own, adding to that bank of guilt is not something I want to do.
Red Pepper is who she is. She would be forming those relationships regardless of whether you & PN were in her life or not. Your being in her life is a highlight of her day, I'm sure, just as having PN & their son in her life is a highlight. Look at the symptoms instead of the full blown illness. It is not your fault if it should happen. Even monogamous relationships have problems, couples split for a time and then get back together and are better than ever all the time.
Each of you holds a special place in her heart. You each fulfill something different in her life. Believe her when she says that she loves you & that if a separation should occur that it isn't your fault. Obviously I only know the portions of the story I've seen on here but I'm getting a sense that all three of you are stressed right now (that one's pretty obvious) and that you all three need a break from the current stress to give your brains a break. Give yourselves permission to take a break from trying to problem solve & have some fun!
I'm sending as much positive energy as I can & wish I could be there to give you all some in person hugs!