Every so often, a random person whom you have never met before is going to come onto the scene and replace someone whom you are very close to. Well, not really, but it will seem to be that way if you happen to be afflicted with a mental illness which is known as the Capgras Delusion. In this disorder of the mind, a person genuinely thinks that some actor or other person has essentially taken over the role in the world of someone who is close to them. There are a couple of different potential explanation for why this would take place (the delusion, not its belief), but none of them are generally curable. It has even been featured in popular culture, due to the potentially interesting interactions that it can bring about between the afflicted and the person they believe is an impostor.
There have actually been several instances of women who have come to believe that their husbands have either left or been taken away from them, while another man who is pretending to be their husband has come around to take his place. While this is almost never the case in anything besides a science fiction movie such as Total Recall, the syndrome makes the entire thing feel just as real as the rising of the Sun or the pain on the wall.
In these kinds of cases, the men who are accused (all of the time) of being nothing more than impostors will either end up leaving for real (since nobody really wants to stay where they are not wanted) or end up in a sort of domestic prison, in which their wives are the warden and they are held captive in a section of their own house, forbidden to enter “her” side. Such a fate sounds terrible, and the fact that other relatives are properly identified simply thows salt on the wound. It’s a terrible fate to not be recognized.