IMAGINE that you and your family have said kaddish all your lives for a relative (or several) who perished in the Holocaust long before you were born. As long as you can remember, you have heard the story of his or her initial escape and eventual murder from the parent or grandparent to whom this ghost was a cherished sibling.
Then imagine that through the combined miracles of chance encounters in foreign lands and the Internet, you have just learned that this long-mourned family member actually survived. Half-way around the world you have a cousin who has also been saying kaddish all these years, thinking it is your relative who was killed.
Based on the family history you and your cousin have known all your lives, you both know that the other can’t possibly exist.