I know this is probably a scary step, but what if you let them read this thread? At the very least it would show both of them that you're sincere and blindsided by this. And what do you have to lose via radical honesty right now anyway, really?
I'm sorry about this turn of events, I really am.
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.