In The Catcher in the Rye, Holden is greatly affected by two deaths: his brother Allie's and a classmate James Castle's. To Holden, Allie was perfect: innocent, uncorrupted by society, a true individual, an artist. As a result, Holden suffers from survivor's guilt and shame for having outlived him: he regrets losing his own innocence. Feelings of rebellion, sarcasm, and sexual confusion rage inside him, and he feels Allie will be ashamed of him for growing up and leaving him behind.
Not only does Holden want to thwart his own maturity and adulthood, he wants to protect others, namely his sister Phoebe. Holden wants to be a "catcher in the rye," a savior to those who are about to cross the threshold from innocence to experience. Holden tries to protect Allie from the sins of the world (he tries to erase the graffito "F@#*"), but he soon realizes it is an exercise in futility.
Holden then wonders if he should commit suicide, like James Castle. Isn't it better to be a romantic rebel-hero (like Castle and Mercutio) and die nobly for a cause? Mr. Antolini warns him that he is ready for a fall:
"The mark of the immature man is that he wants to die nobly for a cause, while the mark of the mature man is that he wants to live humbly for one."
Holden comes to grip with his loss of innocence and confesses all to us in the "rest home." This talk therapy does help even though Holden regrets it:
"...don't ever tell anybody anything. If you do, you start missing everybody."
We know that Holden misses his brother and sister the most, for both are symbols and foil for his own loss of innocence.