I am part of a quad comprised of two married couples. The quad has "officially" existed for just over a year, with friendships running for two or three years before that. We didn't start out looking for a relationship, though; it just developed over time.
I completely sympathize with Jane. Sunday gave me the same speech that she got--"I don't know if I can handle being poly"--and kept me hanging for months after that. Then, just when I was ready to say this is it, I'm ending it, and I was in an emotionally stable zone where I could be okay with Easy (my hubby) and Asha (Sunday's wife) continuing their relationship without me, Sunday started showing me little bits of spontaneous affection. I'm completely confused and at sea.
For now, the quad continues. I can honestly say that I love Easy, Asha, and Sunday. But it ain't been no easy road for me.