What? So you're telling me katherine is a doppleganger of silas's lover and elena is a dopple of katherine? So elna pretty much comes from a chick who steals all the guys from all the sad bitches since 2000 years ago... Talk about Mrs. Steal yo man.
No, they're all doppelgängers of the original progenitor (Silas or Amara). The difference is that once a doppelgänger dies (or becomes a vampire since that's technically dead) a new one will spring up and according to Qetsiyah in Original Sin it was as many had presumed that Stefan is not the first shadow self of Silas, merely the latest.