Rebekah Mikaelson

Rebekah Mikaelson is a free-spirited Original Vampire. She has been a recurring character in Season Three and Season Four. Rebekah was the romantic interest of Stefan Salvatore in the 1920's, daughter of Mikael and Esther and also the only sister of an unnamed deceased brother, Elijah, Finn, Kol and Henrik. She is also the only half-sister of Niklaus. After the death of Henrik, she became the youngest sibling in the family. She used to live in Mystic Falls and had her own house. 

She now lives in New Orleans with Elijah and Klaus. She joined her brothers in the The Originals, having a lead role. Rebekah is the only daughter of Mikael and Esther, wealthy land owners from Eastern Europe in the 10th century. She is the sixth of seven siblings, Elijah, Finn, Niklaus, Kol, Henrik and an unknown older brother who died while the couple still lived in the Old World. Not much is known about Rebekah's early life, other than that she was born in the New World, where they lived in peace among werewolves for twenty years. 

Jeremy Gilbert

Jeremy Gilbert is the adoptive brother and biological cousin of Elena Gilbert and he is a medium. His best friends are Matt Donovan and Bonnie Bennett who is also his girlfriend. Since he came back to life, he's been living in the Salvatore Boarding House with his sister (when she's not at college) and her boyfriend, Damon Salvatore since their house was destroyed by her after his death.

Prior to the beginning of the series, his parents died in a tragic car accident that Elena managed to survive thanks to a vampire, Stefan Salvatore. As a way of coping with the accident, he started dealing and using drugs but soon stopped after the death of his first girlfriend, Vicki Donovan, supposedly because of an overdose. He overdosed on pills after drinking vampire blood in the hope of becoming a vampire and being able to turn off his emotions. He did this following the death of his second girlfriend, Anna. However his attempt to become a vampire failed and the blood healed the damage the pills did.  

He started a romantic relationship with Bonnie Bennett which ended after he kissed Anna. Jeremy was shot by Sheriff Forbes after Damon dodged the bullet and was revived by Bonnie, who is a witch and has connections to dead witches with the power to bring him back. However the spell that caused him to be revived gave him the power to see ghosts and he was haunted by Vicki and Anna. He later went to live with family friends in Denver, after being compelled by Klaus to stand in front of a speeding car. Elena feared for his safety and got Damon to compel him to leave. He returned to Mystic Falls after Elena and Damon went to get him once Klaus found out where he was. He was turned into a vampire hunter and became a member of The Five. After helping Shane free Silas, he was forced by Katherine Pierce to raise the immortal, who then drained him of his blood and snapped his neck. He was able to survive numerous deaths due to the Gilbert Ring, but since he turned into a supernatural being, this death would last. His body was burned inside the Gilbert House because Elena could no longer keep the house after losing the only family she had left. So she decided to burn the house down to make it a good cover story for Jeremy's death. 

Tyler Lockwood

Tyler Lockwood is a main character and hybrid who played for the football team at Mystic Falls High School. He was a werewolf until becoming the first successful hybrid after Klaus.

He is the son of Richard Lockwood and Carol Lockwood, and the nephew of Mason Lockwood who was a werewolf. He was initially portrayed to be arrogant, selfish and a bully. But after triggering the family curse that turned him into a werewolf, he has learned to tone his behavior down. Before this revelation, he was referred to many times as a "dick," by both his best friend; Matt Donovan and Jeremy Gilbert. He is shown to have an athletic build, and great strength as a human. He also has a short temper and becomes angry very easily. He didn't understand why he behaved the way he did, until Mason came to visit after Richard Lockwood's death.

Initially after becoming a hybrid, he was grateful to Klaus for taking away his pain at turning every month however soon becomes angered at the prospect of being sired to him. He manages to break the sire bond and continued to help other hybrids break the curse of being sired. However this came at a price as once Klaus found out his actions, murdered his mother and last remaining family member. Since then, he swore revenge on Klaus for his actions.

Caroline Forbes

"He is your first. I intend to be your last however long it takes." - Klaus to Caroline.

At the beginning of Season 3, Caroline and Tyler started a romantic relationship. It was then affected when Tyler was turned into a Hybrid by Klaus, which created a sire bond that Caroline didn't approve of.

Klaus tells Tyler that he wants him to bite Caroline, he flatly refused but then Tyler accidentally bites Caroline.

Tyler went to Klaus for help and he agreed to save her. Klaus went to Caroline's house to save her and after they had a conversation, he fed her his blood.

Tyler is forced to make a decision on whether he wants his freedom at the cost of having to go through extreme pain to break his sire bond to Klaus. He leaves Mystic Falls, after hurting Caroline caused by his sire.

In Dangerous Liaisons, Klaus then invites Caroline to the ball, and continues to persuade her although she does not reciprocate those feelings, claiming she is spoken for by Tyler. Caroline speaks with Klaus and she tells him that let to Tyler free. They discuss and Caroline ends up leaving the house of Klaus. When she arrives home, she finds a drawing Klaus sketched for her where he thanks her for her honesty.

Later, Klaus expressed a romantic interest in Caroline, who, despite his charm, turned him down several times.