Apparently the Petrova doppleganger is suppose to born every 500 years, which makes sense, but according to Qetsiyah the dopplegangers i.e Silas and Amara versions have been falling in love over and over throughout history. A cute love story
The last episode Original Sin, contradicted several previously stated facts about dopplegangers. In Season 3, one of the Originals said that the doppleganger was created by The Original Witch as a means to break the Hybrid Curse. Obviously this has now either been proven wrong or the writers forgot about that fact.
Another overlooked fact is that Tatia, had a child by an un-named lover, confirmed by Elijah, this could have been a Silas doppleganger, as stated that there were other preceding Stefan and that they are destined to fall in love. But if it were a Silas doppleganger then wouldn't have the Originals said anything to Stefan when they met him, providing that they of course met the un-named lover.
In the 5th Century there most likely would have been the first dopplegangers, they met and fell in love and had a child (which is kinda messed up because that would mean the Salvatore and Petrova lines are related) This is where the timelines screw up, Tatia would have been the last equal timeline events.
When Katherine was born, there was no known version of Silas around, and her un-named lover would not have been a Silas doppleganger otherwise she would have said something to Stefan when they met centuries later. Which brings me to my next point. Stefan was born in 1847, surely there would have been an Amara doppleganger born around the same time so they could meet and fall in love, but on the otherhand as Katherine was a Vampire, the universe must have overlooked another being born because destiny drew Katherine to Stefan. Finally the same thing with Elena, she was born 500 years after Katherine, meaning that there must be a present day version of Silas around that is human, looking for Elena. However as Stefan is now a vampire does that mean the universe cancelled the present day version of Silas?
So my point is that with the Petrova doppleganger being born every 500 years, why is the Silas doppleganger not being born in the same time periods? How can they find each other and live happy human lives if all the dopplegangers only met each other AFTER becoming vampires?