lulululu, No, I have never heard of that condition. However, looking it up online has given me some information on the condition. If you haven't already done so, you might want to go to the "Harvard University Face Blindness Study", for how to best deal with an Alzheimer's patient suffering with that condition.
I think you have a very unique situation, with the other person you believe is one of those husband is confusing you with. You might want to get professional guidance as to how best to handle that one. Or...if you're up to it, just assume the role. Best to you lulululu, hope all goes well, however you handle the situation. Take care of yourself, so that you are able to take care of him, as best you can.