The youngest Fitzgerald child and the protagonist of the novel. Described by her father as their family’s constant, thirteen-year-old Anna is smart, funny, and observant. Anna’s actions drive the plot, as she struggles to reconcile her knowledge that only she can provide Kate, whom she loves dearly, with the organs she needs to survive and her desire to live without this extraordinary burden. While the rest of the family has often been left to sit idly by in Kate’s fight against cancer, Anna, because her genes match Kate’s, has been an active participant. Anna’s role in Kate’s survival has been a blessing and a curse for her, as it has made her Kate’s savior but has also made Anna unable to be her own person.
The mother of the Fitzgerald family. Sara is strong, stubborn, and intelligent, and her life centers on her efforts to keep Kate alive. She has extremely strong maternal instincts, but her single-minded focus on saving Kate sometimes exists at the expense of her marriage and her relationships with her two other children. Even so, she has a deep and abiding love for all her family, though she does not always know how to show that love.
Anna’s lawyer. Initially arrogant and brusque, Campbell gradually emerges as a character with many layers. In many ways, he mirrors Anna. Both have found it difficult to be who their parents want them to be, and both have secrets they are unwilling to share. Campbell struggles between his urge to erect barriers around himself and his genuine desire to reach out to people. He ultimately experiences the most personal growth of any of the characters, and by the end of the story he has formed strong bonds with the people around him.
The father of the Fitzgerald children and a career firefighter. Brian often serves as a foil to Sara. In contrast to her, he can view the situation from his children’s perspectives, making him both more perceptive and understanding than Sara at times. Yet Brian also escapes into his work to avoid dealing with the hardships surrounding his family. He can be kinder than Sara, but by the end of the story Sara proves to be the emotionally stronger of the two.
The oldest of the Fitzgerald children and the most delinquent. Despite his tough exterior, Jesse is in reality a vulnerable and sensitive character. He uses his destructive behavior to mask a fundamental feeling of inadequacy. Jesse cannot save Kate, and he has never been able to forgive himself for that. In addition, he has often felt ignored by his parents, who focus their attention almost exclusively on Kate, and he acts out in part to gain their attention.
The middle Fitzgerald child and the focal point of many of the novel’s events. Kate’s cancer is at the heart of the story, but she only narrates the prologue and epilogue. She has struggled with cancer nearly her entire life, and she appears to have come to terms with the fact that she might die. The reader sees glimpses of the girl Kate could have been, but for the most part her battle with cancer defines her character.
Guardian ad litem to Anna and Campbell’s high-school girlfriend. Julia has a genuine desire to discover what is best for Anna and is one of the most open and caring characters in the story. She possesses an independent personality that made her an outsider in high school but now makes her ideally suited for rendering an objective opinion on Anna’s case.
Julia never truly recovered from the way her and Campbell’s relationship ended, yet she still retains her ability to care deeply about people.
Sara’s older sister. Zanne, a high-powered career woman without children, provides a foil to Sara, who could have been a successful attorney but essentially gave up her law career to care for her children full-time. Zanne often gives Brian and Sara comfort and support. For instance, she watches Anna and Jesse when Sara goes with Kate to the hospital and Brian has to work. Her relationship with Sara offers another example of the unique bond that exists between sisters.
Kate’s oncologist. A warm but serious man, Dr. Chance represents the science and medicine keeping Kate alive. He speaks to Sara and Brian very honestly and directly about Kate’s condition, yet no matter how bleak Kate’s situation gets, Dr. Chance always offers hope that a treatment may work, even when the chances are slim.
The judge appointed to Anna’s case. Fair and kind, Judge DeSalvo genuinely cares for Anna’s well-being. As the father of a child killed by a drunk driver, he understands how desperately Sara and Brian want to keep Kate alive.
Kate’s crush and fellow cancer patient. Kate and Taylor’s short relationship emphasizes that, at heart, Kate is a normal teenage girl. Yet Taylor’s sudden death underscores the fact that Kate’s condition remains extremely fragile and that she could die with little warning.
Julia’s twin sister and roommate. Izzy’s dislike of Campbell reflects how much he hurt Julia, and her presence in the story serves as another example of the extreme closeness that can exist between sisters.
Campbell’s service dog. Campbell does not reveal why he needs Judge for most of the book. Ultimately he reveals that Judge is an epilepsy service dog, meaning he alerts Campbell if a seizure is imminent so Campbell can move to a safe environment.