The relationship between Scout and Jem in To Kill a Mockingbird changes throughout the novel as the characters, particulary Jem, grow up. They experience exciting, upsetting and dangerous events and these help to develop the way they relate to each other.
In chapter one, page one, Lee begins the story by using foreshadowing as Scout recounts the causes of their adventure. She says:
'When enough years had gone by to enable us to look back on them, we sometimes discussed the events leading to his accident. I maintain that the Ewells started it all, but Jem, who was four years my senior, said it started long before that. He said it began the summer Dill came to us, when Dill first gave us the idea of making Boo Radley come out'.
This quote gives us some idea of the way their relationship with each other developed after the story ended. They communicate well as brother and sister while Jem's role as the older brother, a role which he tried to perfect throughout the novel, is evident in his ability to recognise the significance of their initial encounters with Boo Radley.
The age gap between the siblings is interesting as it ensures that their roles in the story are definite; Scout as the curious, young, tomboy and Jem as the increasingly mature, yet rather emotional, older brother. However, despite these distinct roles, the edges sometimes blur. In chapter two Scout's narration tells us of their already changing relationship:
Jem condescended to take me to school the first day...I think some money changed hands in this transaction, for as we trotted around the corner past the Radley Place I heard an unfamiliar jingle in Jem's pockets...Jem was careful to explain that during school hours I was not to bother him, I was not to approach him with requests to enact a chapter of Tarzan and the Ant Men, to embarrass him with references to his private life, or tag along behind him at recess and noon. I was to stick with the first grade and he would stick with the fifth. In short, I was to leave him alone (Chapter 2).
Scout and Jem care about each other, even if they don't always agree with each other. Jem repeatedly talks about being 'gentlemanly' as though the more he says it, the truer it will become. Scout often recognises her brother's emotional reactions to events and gives him time to calm down and process things for himself, showing her own burgeoning reflective nature:
Jem stayed moody and silent for a week. As Atticus had once advised me to do, I tried to climb into Jem's skin and walk around in it: if I had gone alone to the Radley Place at two in the morning, my funeral would have been held the next afternoon. So I left Jem alone and tried not to bother him (Chapter 7).