Yeah, it's a pretty common scenario, as far as I can tell... feelings aren't "supposed" to develop but they're not something people can consciously control, so they do. Great resources at www.morethantwo.com
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.