Dicey's Song explores the growth and development of all the Tillerman children into stable and loving family members, but the novel focuses on the special challenges Dicey faces as the oldest sibling. Dicey arrives in Crisfield as a tough, closely guarded, pragmatic, and highly capable girl. She is used to caring for her siblings, repressing painful truths, and thinking only about things that she can change. She regards Gram with pragmatic eyes, seeing her as someone who understands the Tillermans well enough to live with them, but not necessarily as someone to love. In Crisfield, Dicey suddenly finds herself no longer responsible for her siblings and does not quite know what to make of this new situation. Dicey shuts herself off from her peers at school and begins to work with determination on her after-school job and her boat. However, as time passes, the relationship between Dicey and Gram grows stronger. Gram treats Dicey as an adult and a partner in raising the younger children, even while looking out for Dicey and doing her best to raise her as well. As Dicey becomes reengaged in her siblings' lives, Dicey begins to understand the importance of reaching out, and she consequently follows her grandmother's lead and begins reaching out to her peers as well. Dicey uses the strength garnered from her bonds with others to face the biggest challenge yet of her life at the end of the novel.
Gram resembles her oldest granddaughter, Dicey, quite closely. She is independent, practical, scornful of social conventions, and completely self- sufficient. Like Dicey, Gram, throughout the course of the novel, learns to let go of her past and to reach out to those around her. Gram lives with the dark consciousness of the harshness and bitterness of her past. She married a rigid and unloving man and stood by him stubbornly as his coldness alienated and drove away each of their children. When the Tillerman children arrive on her doorstep, Gram's deepest reluctance to take them in stems from inability to face the choices she made in the past, to share them with the children, and to risk making them again. However, she courageously decides to take the children as her own, and the determination and conviction with which she makes the decision drives her through the entirety of the novel. Gram is not emotionally effusive and affectionate with her grandchildren, but her actions and the meaning behind her gruff demeanor clearly demonstrate her devotion to them. She reaches out to each of the children, striving to help them to solve their own problems, but especially to Dicey, upon whom she relies for help and who she herself counsels about the importance of being emotionally involved in her family's life. Gram herself is not immediately and completely open with her grandchildren. She closely guards the attic, which contains photo albums and other reminders of the past, and she does not share the details of the letters from the mental hospital in Boston with them. By the end of the novel, however, Gram has begun to open up the past to her grandchildren and share not only the wisdom she has gained through her mistakes, but the stories of the past which the children long to hear.
James is a pensive boy confident of his mental capabilities but less confident of his social standing among his peers. Of all the Tillerman children, James suffered the most greatly at being an outcast as a result of Momma's unconventional lifestyle, and he more than any of them sees Crisfield as a chance to start over without the dark cloud cast by Momma's well-known eccentricities hovering over them. Dicey has always worried about James's ability to divorce himself from morality or emotion with his intellect, and his ability to use his intellect to find means to his own ends. James faces two major challenges in the course of the novel, both of which illustrate his shortcomings and his strengths. First, James wants to make friends, and to do this, he learns to act as though he is not as smart as he is in school. The boy he befriends, however, is also a cerebral and scholarly boy, and James does not have to change his interests and activities in order to be the boy's friend. Second, James assumes the responsibility of helping Maybeth learn to read. At first, he shirks this responsibility in favor of spending more time pursuing friends, but in the end, he applies his mental keenness to Maybeth's problem with skill and perseverance. James works to balance his desire to be well liked with his desire to be a loving and responsible member of his family.
Dicey's only sister, nine-year-old Maybeth is in the third grade, having been held back in Provincetown. Maybeth, like all the children, suffered at the hands of her disapproving peers, and responded, unlike Dicey or Sammy, by drawing deep into herself and becoming deeply afraid of interacting with others. Maybeth is meek, quiet, and hardworking, but her fears and her sense of confusion over Momma have made it difficult for her to learn in school. Unlike her siblings, Maybeth tries dutifully to do as she is told without questioning or strategizing, and consequently, she works diligently on exercises in a manner that does not help her. Dicey deeply respects Maybeth's ability to remain patient and loving in all situations, a characteristic she shares with Momma. All of the children admire her musical ability. Maybeth proves her mental capacities by becoming an adept pianist, and her success at piano gives her comfort and strength. By the end of the novel, she seems more sure of herself, timidly telling Gram that a note from her teacher probably has good, and not bad, news.
The youngest Tillerman, Sammy is stubborn and hardworking like Dicey, but also the main source of humor and laughter for the family. He also is fiercely devoted to his family members and will go to any ends to protect them or to keep them together. Sammy swings from being as meek and mild as Maybeth at school, fearing that if he behaves badly he will drive Gram away (as he suspects he drove Momma away), to fighting frequently in response to the schoolchildren's jibes about Gram's oddness. He fights Dicey when she ignores or is dismissive of him, but he thrives under her attention and respect. Because of his age, Sammy has the most difficult time reconciling himself with Momma's condition, and throughout the novel he speaks wishfully of her recovery and return.