You've heard of the Mikaelson family, you've heard of Finn, Elijah, Niklaus, Rebekah, Kol, and Freya Mikaelson. The one no mentions is the second eldest daughter Emily, after Freya and before Finn.
She too was made a vampire by her mother and father, Esther and Mikael, but she didn't last long. After Klaus' parentage was reveled, they bound his werewolf side, but the spell required the sacrifice of someone whom shared his blood.
Now I know what you're thinking they turned their children into vampires to keep them from being killed, yes that is true however Esther did not want to upset nature further by letting Klaus posses so much power. Emily and Klaus were fathered by the same man so Emily was made the sacrifice.
Disclaimer I do not own the vampire diaries or the orginals or any of the characters except for my own. I also use scenes from the actual shows. Again I do not own the vampire diaries or the orginals this is just me having fun and letting my imagination go wild. I do not own some of the plot in this story I'm mostly following the plot while adding my own creative touch.