The Cullens are Edward’s vampire family. Family members have all been "adopted" by Carlisle Cullen, the head of the family, and include his wife Esme, Edward, and the couples Alice and Jasper, and Rosalie and Emmett. For a more detailed analysis of the Cullen family, check out "Characters" in our guide to Twilight.
Carlisle formed the only known vampire family that feeds on exclusively on animals, rather than on humans. Although he created his wife and children by transforming them into vampires, Carlisle did it to save them from dying. In fact, in Edward’s case, we learn that Edward’s mother begged Carlisle on her deathbed to "save" Edward. She apparently knew that Carlisle was a vampire.
Carlisle tells Edward’s story to Bella while he tends to her wounds after her ruined birthday. Carlisle is immune to the smell of human blood since he has been working at a hospital as a doctor for over 300 years. He loves his work because he believes that, by healing others, he’ll redeem his evil nature as a vampire.
In contrast to the rest of the family, including Edward, Carlisle thinks that there’s an afterlife for good vampires. Carlisle not only votes for Bella to become a vampire, but also promises to change her after her graduation, if Edward won’t.
Through the events that unfolded in Twilight, Alice and Bella have become close friends. They’re very comfortable around each other. It seems that, like Edward, Alice possesses considerable self-restraint when it comes to her killer instinct around humans.
Alice also has a special ability: she can see the "planned or subjective" future. After Edward breaks up with Bella, Alice keeps checking up on her through her "visions," and sees Bella jump to her apparent death. Alice accompanies Bella to Italy to save Edward’s life. Alice clearly thinks that Edward and Bella should be together, because she tells Bella that she’s been debating whether or not she should transform Bella into a vampire herself. She also votes in favor of Bella becoming a vampire in the end of the novel.
Since Alice has no memory of her human life, she shares with Bella that she researched her family and visited her own (fake) grave. Alice’s parents evidently sent her to an insane asylum the same day they declared her dead. She doesn’t know what to make of it.
Rosalie never wanted to become a vampire, but she had no choice. That’s why she’s jealous of the human Bella from the beginning. When she learns about Bella’s alleged suicide from Alice, she goes out of her way to tell Edward. Rosalie feels horrible about it later, and asks Bella to forgive her. Her regrets about becoming a vampire lead Rosalie to vote "no" on Bella’s transformation during the Cullen family meeting.
Strong, big, and always in the mood for trouble, Emmett is gung-ho about saving Edward, but he listens to Alice’s advice to stay back and let Bella do the job. He genuinely likes Bella and also votes for her to become a vampire. After leaving Forks with Rosalie (partly because she doesn’t like Bella), they’ve been traveling around Europe, then return to Forks after Edward is saved.
Poor Jasper. He evolved into a "vegetarian" vampire to become part of the Cullen family and, although he seems to try very hard, he still’s very much susceptible to the delicious smell of human blood. He’s torn up about attacking Bella on her birthday. In many ways, Jasper’s loss of control triggers Edward’s decision to break up with Bella to keep her safe.
Esme, the matriarch of the Cullen family, adopted Bella into the family from the moment she met her. Although Esme’s not Edward’s real flesh and blood mother, she looks like "she would be crying if that were possible" (22.111) when she holds Edward safe in her arms after his suicide attempt. Esme roots for Edward and Bella to be together, and also votes for Bella to become a vampire.