Sirelines

A Sireline is a figurative bloodline of vampires or hybrids and the chain of those by whom they have been sired. If the originator of a bloodline is permanently killed with a White Oak Stake, or by other means, everyone in their bloodline dies within a few hours. It was a powerful and sophisticated link added to the immortality spell by Esther as a method of further protecting her children.
Rebekah and Kol are the two living Originals with and without a sireline, respectively. As such, all remaining vampires are either from Klaus' unlinked sireline or from Rebekah's sireline. Following his resurrection, it remains unknown if Kol has turned any other vampires. There is yet to be any vampires sired from an Enhanced or an Upgraded Original vampire.