"Jeff and Mary" or "Mary and Jeff"? Which name do you put first, the person you knew first? The person who you know/like better? Whichever sounds best?
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If you kind of knew Jeff for a while, but then became good friends with Mary, would it be kind of rude to call them "Mary and Jeff"? Or do you not get the order of a couple's names fixed in your mind at all, and vary it at your whim?
I think I would pretty much always put the person I knew longest in first place. I can think of one couple where I became really good friends with Jeff, and "Mary and Jeff" became "Jeff and Mary", even though I had known Mary for many more years. I can even remember a transitional period where I switched back and forth.