(I don't think that was a total hijack...)
I'd wager it happens to most people who have more than one lover, even serial monogamists. (me, I can't even remember MY OWN name sometimes - but I've changed it, twice)
My step-mom used to call my dad by her first husband's name a lot. (although he'd get yelled at if he did the same)
FBF's name starts with the same syllable as my high school bf. I flub that from time to time.
When my family had a house full of people, my mother would run down the list of names until she got to whomever she was trying to call. I got called by the name of her childhood dog more than once. Kippy. Yah, that doesn't sound anything like my name.