Good discussion, even if the OP doesn't seem to be "getting it."
In my case, I've got a live-in gf. We've been together 5 years and living together less than a year. We share finances, but are not raising kids (mine are grown and she can't have any).
My bf of 2 years is married, has been with his wife for 20+ years. I guess technically, then both my bf and I have "primaries," but it doesnt impact how we feel about each other. We do have to manage our time together dependent on needs and wants of our other partners, seeking balance, not equality.
I do not feel "committed for life" to either, like some kind of life sentence! I get along quite well with both partners. I reckon I will be partnered with each one for a long time to come. We work hard at ironing out differences and respecting each others' desires and needs. I wouldn't dump Ginger just because miss pixi wanted me to.
That said, when Ginger recently started dating other women, I did have issues with his choices. But I am working hard at dealing with him adding new lovers into his life. It hasn't been easy, but its his right, and I want to support it. You can read my blog here, the last dozen or so posts show the work we had to do. I've had a lot of other life stresses lately which made dealing with him dating harder than it should be.
Love withers under constraint; its very essence is liberty. It is compatible neither with envy, jealousy or fear. It is there most pure, perfect and unlimited when its votaries live in confidence, equality and unreserve. -- Shelley
me: Mags, 59, living with:
miss pixi, 37