Ugggg. All sorts of convolutions in order to position characters as being either the same, or related by bloodline. It's messy. If character A and character B meet and they are the same person from different times in their lives, one would have memories of the other. And why can't 21st and 25th century scientists do simple DNA analyses? "So, Rama, can you give me the name of your plastic surgeon so I can save a lot of ... time.