OverviewElijah Mikaelson is the deuteragonist of The Originals. He was formerly a major recurring character in The Vampire Diaries, serving initially as an antagonist in the second season and eventually becoming a supporting character in the third season and fourth season. Elijah is an Original Vampire.
Elijah is the son of Mikael and Esther. He is the younger brother of Freya Mikaelson and Finn Mikaelson, and the older brother of Kol Mikaelson, Rebekah Mikaelson and Henrik Mikaelson. Elijah is also the half-brother of Niklaus Mikaelson and the uncle of Hope Mikaelson, Klaus' daughter with Hayley Marshall.
Throughout his long life, Elijah has had a few romantic relationships. In the 10th century, Elijah and Klaus were both in love with a Petrova Doppelgänger named Tatia. Upon their transformations into vampires, Elijah accidentally killed her, greatly shaking him. After seeing him kill the woman he loved, Elijah's mother told him to seal the event behind a 'red door' and to clean himself up; as long as he was clean, nothing of what happened behind the red door could hurt him. As such, this became Elijah's defense mechanism to cope with the horrors of his vampirism for the next thousand years. In the 15th century, Elijah was romantically involved with another Petrova Doppelgänger, a young girl from Bulgaria, named Katerina Petrova. In the 19th century, Elijah was romantically involved with a witch named Céleste Dubois, whose death was later caused by his half-brother Klaus. In the 21st century, Elijah rekindled his relationship with Katerina Petrova aka Katherine Pierce, before ending it to go to New Orleans to help Klaus. In New Orleans, Elijah has developed feelings for Hayley Marshall, after he promised to protect her and the child she was carrying. Since then he has kept his distance considering she is now married to Jackson Kenner.
Elijah has the closest relationship with Klaus, who he wishes to maintain a good relationship with. The two live and work together to defeat their enemies in New Orleans. In the second season of The Originals, Elijah continued to work with Klaus in effort to stop Esther, a revived Finn and a revived Mikael. He also took Gia, one of Marcel's vampires as his protégé, whom he had a romantic relationship with.
Elijah is a member of the Mikaelson Family.
-taken from The Vampire Diaries & The Originals Wikia