Holden loved his brother very much. He wants to be to someone, what Allie was to him. Holden keeps everything inside, yet when his brother dies, we see a side of Holden that is deeply real.
Allie was eleven years old when he died. He was two years younger than Holden. Allie had leukemia and died from this. As Holden thinks about his brother, he says that he was the most intelligent in the whole family. He also says that he was the nicest and sweetest kid ever. The night that Allie dies, Holden sleeps in the garage and broke all of the windows out with his bare hands. Holden ends having to be hospitalized for this. He sees Allies as almost a saint now. We can see that the death of his brother, affected Holden greatly. He still talks to his brother and still thinks about him. Holden probably never got any help with dealing with his feelings over Allie's death. He almost glorifies Allie now. Holden's reaction to his death, shows us that Holden reacts to tragedy, by harming himself. He probably does this, because it is easier to deal with physical pain than to deal with emotional pain.
Throughout the entire novel, Holden struggles to keep focus on the future. He can't do it. He lives in the past. When Holden goes back and thinks about the death of his brother, we see how the emotional scars of the past still dictate our future. Holden's behavior over the death of Allie, is the same behavior he has anytime things go wrong in his life.