Born to Mikael and Esther, Eastern European immigrants who settled in Virginia
His father was a controlling, vicious man who raised his children to be violent and aggressive, each of them possessing different strengths and weaknesses
Klaus fought to try and protect his siblings, eventually killing his father to protect himself
Was invited to join the organization shortly after finding himself alone with his siblings scattered to the four winds (*see below)
Freya: missing since childhood, Klaus is still looking for her
Finn is still with Freya and working with her in her apothecary. Klaus goes to them when he needs any sort of chemical or medical concoction
Elijah: A director of the Organization, but Klaus doesn't easily tell people that.
Klaus: Not Mikael's child
Kol: Currently in prison for spree killings
Rebekah: Runs a club in New Orleans with her partners, Marcel, called the Abattoir
Niklaus Mikaelson - Theseus