Jacob's older sisters, Rachel and Rebecca Black, are never mentioned in the films.They're twins that are about a year older than Bella Swan.Since Rachel is on scholarship at college and Rebecca is married and living in Hawaii, they're rarely a part of the books' plots either.Jacob's mother died before the start of the first Twilight book in a brutal way.He reflects on her death in Breaking Dawn, which finally gives readers more information about what happened.Jacob mentions his mother died in a car accident that left her body so mangled she was buried in a closed-casket ceremony with her coffin nailed shut. In the first Twilight book, Jacob appears as a minor character that introduces Bella to the cold ones lore about the Cullen family.But author Stephenie Meyer made the decision to expand Jacob's story when she realized how much she liked the character.On her website, Meyer described the process of writing the werewolf as the first experience with a character taking over, adding he developed such roundness and life that she couldn't keep him locked inside a tiny role.In New Moon, Jacob tells Bella what it's been like for him to adjust to being a werewolf.He mentions that he finds it easier to phase back and forth than the other wolves, which he believes is because of his ancestry.Both of Jacob's great-grandfathers were werewolves, so he has supernatural blood on both sides of his family.When the werewolves in Twilight turn for the first time, they physically grow very quickly before halting the aging process altogether until they're significantly older. Because of this, Jacob has the body of a 25-year-old when he's a high schooler.The sudden growth spurt is also why he's so tall — it's revealed in Eclipse that Jacob stands at 6 feet and 7 inches. Most of the werewolves in Sam's pack seem enthusiastic about their abilities, but in Eclipse, Jacob tells Bella that he and Sam Uley are the only ones who dislike it.Sam doesn't like how imprinting and accidentally losing control of his temper have impacted his relationships.On the other hand, Jacob resents his powers because he never chose to become a werewolf and feels like he was roped into a supernatural war he previously didn't know existed.Jacob's father, Billy Black, didn't use a wheelchair until some time after his wife died.By the time Billy started needing one, Jacob's sisters were already older and spending less time at home.So Jacob helped his dad care for their household, which he didn't seem to mind since they had a close relationship.In Eclipse, Jacob tells Bella that since his great-grandfather, Ephraim Black, was the last chief of the Quileute tribe, Jacob was supposed to be the alpha of the werewolf pack.Jacob deferred to Sam, but later became the alpha of his own pack.When he breaks away from Sam's pack in Breaking Dawn, Seth and Leah Clearwater follow Jacob and recognize him as their alpha.In Meyer's original idea of Twilight as a standalone novel, werewolves weren't going to be part of the story.Even though the legends Jacob tells Bella mention them, the vampires were intended as the only relevant part of those stories.On her website, Meyer wrote, The dream Bella had of Jacob transforming into a wolf to protect her had no foreshadowing significance at the time. It was just my way of letting Bella's subconscious articulate the situation.She added that the image stuck with me while writing New Moon.Jacob's sister Rachel comes back from college before Breaking Dawn.When she does, Paul Lahote imprints upon her, and Rachel is told about the existence of werewolves and Jacob's role in the pack.This adds to Jacob's disdain for the imprinting process.Jacob was distraught after finding out Bella and Edward were engaged.After surviving the battle in Eclipse, Jacob considered living permanently as a werewolf to avoid having to see Bella be turned into a vampire.Although he only ended up staying a wolf for about two months, it's mentioned that this decision is possible, as other werewolves in the past lived entirely in their bestial form.Bella's health deteriorates while she's pregnant in Breaking Dawn.Thinking about how her future child will crave blood, Jacob is the one who suggests the Cullens have Bella drink human blood to feed the fetus and herself.His idea works and is part of how Bella survives her pregnancy long enough to be turned into a vampire.During the confrontation with the Volturi in Breaking Dawn, Edward reveals that the Quileute tribe members who can transform into wolves are not werewolves in the Twilight universe.Edward explains that true werewolves, which the Volturi call Children of the Moon, cannot transform during the day, rarely exist in packs, and have the ability to turn others.Instead, Jacob and the other members of the pack have a genetic shape-shifting skill that manifests in their wolf forms.