At the beginning of the novel, Jem argues with Scout and constantly bosses her around. They have a typical sibling relationship, where Jem is the older brother and continually tells Scout what to do, which leads to many arguments. Despite Jem's antagonistic personality towards his younger sister, he cares about her well-being and even shares some of his birthday money with her. Scout also looks up to Jem and believes everything he says regarding Boo Radley.
As Jem matures, he becomes more distant and begins hanging out with Dill more than Scout. Scout resents the fact that her brother spends most of his time with Dill and is forced to hang out with Miss Maudie. While Jem is maturing into a young man, he becomes more authoritative towards Scout and views her as a naive child. Scout resents Jem's "maddening superiority" and fights with her older brother often. Jem believes that he knows more than Scout and attempts to treat her like she is inferior. Even though Jem is physically growing, he still thinks like a child, which is depicted in the way he treats his younger sister.
Following the Tom Robinson trial, Jem loses his childhood innocence and begins to express sympathy for others. Jem becomes more understanding of Scout and views himself as her protector. Jem develops into a morally-upright individual like his father and comforts his sister when she gets upset. Jem prevents her from arguing with Aunt Alexandra and even attempts to explain Maycomb's caste system to Scout. Jem also volunteers to walk Scout to the Halloween festival and protects her during Bob Ewell's attack. Overall, Jem treats Scout better and exercises sympathy towards his younger sister the more he matures. Jem's compassion towards Scout reflects his maturity and moral development as a young man.