In To Kill a Mockingbird, the Finch children spend a lot of time together, and if they have friends other than Dill, the reader does not meet them. Jem and Scout are very close and in general get along well. Although Jem often treats his sister harshly, he does everything in his power to save her when Bob Ewell attacks them, breaking his own arm in the process.
As the children get a little older, the age difference between Jem and Dill seems less important to Jem than the gender difference between the two boys and his little sister. Jem does not want her hanging around him at school. On her first day, he makes it clear that she should not intrude into his social circle. However, he assures her that at home they can still play together.
Jem tends to use “girl” as an insult, indicating that he has a lower opinion of girls. When Jem and Dill begin to spend more time together, this bothers Scout because she and Dill were formerly close; in fact, they are engaged. When they play their Radley game, the others try to give her the worst role. Sometimes Scout chooses not to participate in the boys’ activities, and when Jem wants to sneak up to the Radley house, she questions the wisdom of doing so at night. Annoyed at being challenged, Jem snaps:
Scout, I’m tellin’ you for the last time—shut your trap or go home—I declare to the Lord you’re gettin’ more like a girl every day!