What influences the order of names in a couple?

[DapperButch]

I think that June hit the nail on the head for me when she said that in some cases it is a function of who I have the primary relationship with.

For my sister and her husband, I use her name first, for example.

In thinking about my relationships with same sex couples, I think it is a function of primary relationship, but is also a function of what I hear others call the couple, or sometimes is simply a function of what sounds most pleasing to my ears <shrug>.

These are my best guesses, anyway.

P.S. Most of my same sex couple friends are androgynous, with neither being more masculine than the other.