If these are both solid, happy relationships, why do you want to leave? It's great that you've realized you don't NEED them to be happy, but that doesn't mean they aren't wonderful things to have in your life, yeah?
What do you think you will gain from being single versus what you stand to lose in terms of love, family, and support?
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.