In the USA, where I live, it is becoming increasingly common that men and women are making committed relationship decisions, but choosing to remain unmarried. However, they live together, raise children together, and otherwise appear married. They are simply not legally married and they are okay with it and so are most other Americans. It is obvious that they are highly involved with each other and the depth of their relationship is akin to a long standing marriage.
I am having trouble determining what to call men and women in this kind of relationship, relative to the other. I might say "my friend's girlfriend," however, I would also use this same term for whatever the relationship of two 14-year-olds is. It seems to me that my friend and his relationship with his girlfriend deserves higher recognition.
Lately, I have resorted to calling these women ladies. I might ask my friend "How is your lady doing," or say about a party "Bring your ladies." I like this because the definition of lady implies a high 'social' status and removes any negative connotation that the women are morally devoid because they are not married, yet live with a man. Oddly, someone told me recently that it sounded sexist when I referred to a few friends and "their ladies." I don't even really know how to approach that.
It wasn't until just now that I have no ideas at all for men. Just "lady" for women.