Klaus Mikaelson.

Klaus was the oldest vampire in history. Elijah later mentions that Klaus is a loner and trusts very few people, usually only those in his inner circle. And for that reason he was the oldest vampire in history, the one who could never be defeated. Sometimes family is death. Love is death.

Many years earlier, his mother had an affair with a man from their neighboring village, whose inhabitants were known to be werewolves, men who transformed into wolves on the nights of the full moon. Niklaus has six half-siblings fathered by his stepfather Mikael, a Viking warrior and wealthy man who moved with his wife, Esther, to the New World after their home was destroyed by a plague. Mikael believed his beloved firstborn Freya had fallen victim to the plague, unaware that she had been taken by Esther's sister Dahlia as payment for a fertility spell that allowed Esther to bear children. Klaus was very close to his family with the exception of Mikael. Mikael was excessively harsh towards Klaus, having become an aggressive, violent and strict man after thinking Freya had died, always trying to teach his children how to survive as he did not want to lose another child. In Klaus' case, Mikael was abusive towards him for his impulsive and reckless behavior, justifying that his punishments would make Klaus stronger, but Mikael only felt disappointed in everything Klaus did and repeatedly beat him throughout his mortal life.