Is a doppelganger an evil version of someone or can it be a double of the person (as in bilocation)?

eg,, in dr jekyl and mr hyde, mr hyde isnt a double of jekyl, but he IS the same person... Sometimes when someone is extremely kind, they are at another time extremely cruel. Almost as if the cruelness has to play out in order to balance the overbearing kindness. Is hyde a doppelganger of jekyl?? (please no WIKI, thanks)Is a doppelganger an evil version of someone or can it be a double of the person (as in bilocation)?
A doppleganger is simply someone who resbembles who looks ALOT like another person. It has nothing to do with personality.

good makeup