What passages in To Kill a Mockingbird show the strong brother-sister relationship between Jem and Scout?
In Harper Lee's To Kill a Mockingbird, Scout and Jem have a very close brother and sister relationship. Though they drift apart a bit as Jem grows up, they in general remain close.
We see evidence of their closeness in the very first chapter. After opening the book by relaying Finch history, Scout describes what Maycomb is like, describes a little about her own family, and describes their neighborhood summer boundaries when Scout was 6 and Jem was 10, the same summer they met Dill. Scout then goes into a narration of the day they met Dill:
Early one morning as we were beginning our day's play in the back yard, Jem and I heard something next door in Miss Rachel Haverford's collard patch. (Ch. 1)
Scout's choices of words in the clause, "we were beginning our day's play," are very revelatory because they show just how frequently Scout and Jem play together. They play together so often that playing together is a natural occurrence in their daily lives during the summer. The fact that they spend so much time together shows us just how close they are as brother and sister.
However, as the novel progresses and Jem grows older, Scout and Jem grow apart. Dill is the first to influence Jem in a way that drives a wedge between Jem and Scout. Dill influences Jem to try and make Boo Radley come out of his house, which Scout disapproves of, so she starts spending a lot of time that summer with Miss Maudie while the boys go off on their own. On Dill's last night in town, he encourages Jem to sneak onto the Radleys' property with him and try to get a look inside through a window. When the children become frightened and must run, Jem gets his pants caught on the Radleys' barbed-wire fence and must abandon them. He later decides to sneak out at 2 a.m. to retrieve them. Scout is absolutely horrified by the idea because she thinks Jem's life will be in danger if he goes back on the Radleys' property, but Jem is determined because he feels a sense of guilt for having sneaked onto their property in the first place and doesn't want Atticus to find out what really happened. Scout begs him not to go because she is too young to understand his sense of guilt. Since she can't understand Jem's reasoning, she says to herself, "It was then, I suppose, that Jem and I first began to part company" (Ch. 6). The fact that she feels like she and Jem are parting ways shows us she and Jem are beginning to grow apart because they are growing older.