I don't think of myself as coming from 2 + 1, but perhaps it technically was. I dated FirstBoyfriend, we were both friends with CurrentBoyfriend. I broke up with FBF, and a few months later, started dating CBF. Threw CBF out of the house, said we were breaking up (took two months from conversation to out). Then we slept together. Then we went on vacation together. Then FBF confessed his desire. I sought consent from CBF, but I wouldn't exactly say permission. I'm not sure we could do this if I was living with CBF again. (not that I want to).
So, I was a two with each of them first. Now we are a three.
Love is that condition in which the happiness of another person is essential to your own...
Robert A. Heinlein
Me: female, bi, (formerly hinge of a vee)
with FirstBoyFriend (FBF)(moderately long-distance)
and no longer with CurrentBoyFriend (CBF)(who now lives in a house far away-with stairs I can't climb)