I would like to add D (from Vampire hunter D) to the argument. D and CV Alucard have much in common with both of them being dhampires, immortal, fighting vampires, very little is known about both of them, and both of them are very powerful (D, as portrayed in Bloodlust, is far too powerful IMO).
Also... if you consider the fact that both are the sons of Dracula you can say they are practically the same person.