Jeannette Walls is the author and protagonist. She is the second-eldest daughter in a family of four children. Her self-absorbed and clown-like yet highly intelligent father and mother are arguably mentally ill in their refusal to live by any of society’s norms, a choice which renders them unable to adequately provide for Jeannette and their other three children. Jeannette is strongly characterized by her ability to love and forgive others while also learning from their mistakes, however during the first chapter of the book Jeannette chooses to ignore her homeless mother, prompting the flashback which reveals the complexity of their difficult relationship through-out Jeannette's childhood. Jeannette chooses to remain optimistic and maintains a positive view of her life and the people around her. Jeannette often felt less sympathy for her mother, preferring to view her father as an unusual sort of hero despite the countless times his selfish actions hurt their family. Jeannette forgives her father in the end and ultimately finds forgiveness for her mother as well.
Rex Walls is Jeannette's father and the founder of the idea "The Glass Castle". Rex intends to build a glass castle for his family of six with the money he is convinced that he would receive upon finding gold. He refuses to abide by even the most basic of society's rules and instead chooses to live selfishly, guided by his exaggerated and unrealistic dreams. Rex is portrayed as exhibiting many signs of mental illness and alcoholism; he is very intelligent but not in any tangible way, he is an "excitement addict", he is constantly shirking his responsibilities, he makes promises that he doesn't keep, he seems to have an over-inflated sense of self, he continually (consciously or subconsciously) sabotages many positive developments in his life or the life of his family, he has extreme difficulty in adequately providing for his family despite his professed desire to do so. The reader is given insight into a possible contributing factor of Rex's dysfunctional behavior when it is revealed that his mother Erma had tried to abuse Rex's son Brian by touching him inappropriately, indicating the potential extent of the cruelty his mother had shown toward Rex as a child. Despite all of his shortcomings, Rex manages to keep his children healthy, get them a quality education, and he brings his children great joy by "giving" them unrealistic presents, such as a star in the sky. He never abuses his children (although depriving his dependents of their basic needs is arguably abusive) and he always keeps their hope alive. He is portrayed by his daughter Jeannette as a very charismatic man who is deserving of her frustration but also of her sympathy as she attempts to understand him.