Thanks everyone for your input so far. Apparently it does happen more than I thought. I'm glad to see that.
Originally Posted by XYZ123
As I said, my husband and I started off open. Maybe we weren't technically single as we were each dating others. But we didn't consider either of us were "joining" an existing relationship since I didn't know his other gf and he didn't know my other bf.
I had a similar situation, but I can see your point about how it's really no different from starting as two singles.
Strangely I always look at it like I'm becoming a secondary because her other love has seniority, and yet I never really pick a favorite/primary for myself. Maybe I should relax more when going into these things.