It is revealed that Elena is a Petrova Doppelgänger (like Katherine, Amara and Tatia), which is thus responsible for her being identical to her ancestor, Katherine Pierce (née Katerina Petrova). This also has the implication of making her a supernatural creature.
Katherine gave birth to Nadia, who also had a child. That bloodline eventually lead to the Flemming family (Elena's birth mother). Isobel Flemming gave birth to Elena. So, Katherina is Elena's ancestor.
It wasn't until the 21st Century that a human Doppelgänger was found: Elena Gilbert. So not including Amara there are ONLY three known Doppelgängers in her line: Tatia, Katherine and Elena.
Once Elena drank the Cure, Damon planned to feed on her, and as long as nobody sucked it out of him, he and Elena could live the rest of their lives together as mortals. Unlike Katherine, Elena wouldn't be affected by having the Cure removed to her blood as she'd only been a vampire for a short time.
However, it turned out, Katherine and Elena shared the same mother, making them half-sisters. In the series, Elena Gilbert is a distant descendant and doppelgänger of Katherine Pierce. Katherine is Elena's first kill in the books and the first vampire destroyed in the novels.
Elena Gilbert (3rd Petrova Doppelgänger): Elena was born on June 22, 1992, in Mystic Falls, Virginia. She was the biological daughter of John Gilbert and Isobel Flemming, and was therefore a descendant of Katerina Petrova, to whom she bears a striking physical resemblance.
Isobel Flemming was the wife of Alaric Saltzman and the biological mother of Elena Gilbert. She was good friends with her ancestor Katherine Pierce, a vampire she often conspired with. When Isobel was still in high school, she met John Gilbert and became pregnant with Elena.
Damon is also now human, following Stefan's decision to inject his brother with the cure in The Vampire Diaries series finale. That's how Damon and Elena had their daughter, Stefanie Salvatore, named in memory of her hero-haired uncle.
Krystal was a vampire who was turned by Julian and was part of his army that resided in Mystic Falls. She has a one night stand with Damon Salvatore after he tries to get over Elena Gilbert's supposed "death."
Cure took Silas's Immortality, he was affected. He didn't aged to his biological age because he took every drop of Katherine's blood (aka Cure).
Elena is adopted and so people incorrectly assume that she is not related to Jeremy, however Elena's biological father is John Gilbert, Jeremy's biological uncle, thus making Elena and Jeremy biological cousins and therefore related.
Tatia is the first-known Petrova doppelganger, and her blood was used by Klaus' mother, Esther, to turn her children and husband, Mikaelson, into the first vampires. Following suit is Katherine Pierce, and the modern-day heroine, Elena Gilbert.
It is revealed that Elena is a Petrova Doppelgänger (like Katherine, Amara and Tatia), which is thus responsible for her being identical to her ancestor, Katherine Pierce (née Katerina Petrova). This also has the implication of making her a supernatural creature.
His immediate response: “Oh, yeah, isn't that my daughter?” Indeed, Stefanie Salvatore — as referenced during a Season 1 episode of The CW's Legacies — is the daughter of Elena Gilbert and Damon Salvatore, named in loving memory of the late, great Stefan.
Throughout The Vampire Diaries
In the season four finale of The Vampire Diaries, Graduation, Katherine slept with Niklaus Mikaelson and conceived her daughter, Adyelya.
The two of them discuss what happened between Stefan and "Elena" and Caroline also tells him about Nadia and Matt and the text he sent to her. From Matt's text, who used "K" and not "E", they put the pieces together and they realize that Katherine is in Elena's body.
And yes, the show later confirmed that Damon and Elena have multiple children - Jenna, Sarah Lillian and a son, Grayson.
In an Instagram post shared by the 31-year-old actress, after saying goodbye to the show, she stated that she decided to leave it because she felt like Elena's journey had come to an end. “I always knew I wanted Elena's story to be a six-season adventure, and within those six years I got the journey of a lifetime.
Elena initially rejects the cure, but Damon decides to take it with her so that they can have a human life together, including children. Damon always wanted Elena to have the human life she always dreamed of. Elena takes the cure, which breaks the compulsion, and her memories of Damon return to her.
While Damon and Elena (Nina Dobrev) fans were dealt a pretty devastating blow in last week's episode, with Damon burning Elena's body and all, Damon drove the stake in the Delena fanbase's collective heart even further when he hooked up with someone else. Yep, it finally happened, and we were NOT happy about it.
The Vampire Diaries was a popular series that aired on the CW. It made changes from the books, such as Bonnie and Damon not dating. Bonnie instead ends up in a romantic relationship with Enzo toward the end of the show.
Isobel Flemming was the biological mother of Elena. She was turned into a vampire by Damon Salvatore by her insistence. She became cold and calculating, but wished for her daughter to live a normal life. She was compelled by Klaus to find Elena, use Alaric as a host, find a vampire and werewolf for his ritual.
Alaric is Elena's step-father and second legal guardian after Jenna. Alaric drank Elena's blood to become a vampire. Elena once killed Alaric, though she did so only to ensure he would return to life while wearing the Gilbert ring.
Alaric/Klaus takes Elena and Bonnie away and reveals them that he is Klaus.