Is anyone else confused with the whole Silas situation?

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I have seen every TVD episode to date, and upon seeing the latest episodes, I got a little lost. I thought Esther created the very first vampires, them being her children, and now we hear that Silas is buried with a cure. If Silas is so much older than the Originals, how is it he has a cure for vampirism, before there even was vamirism?!?