Holden informs us that his brother D.B. is a great writer (his personal favorite piece is a short story, "The Secret Goldfish," about a boy who won't let anyone look at his pet goldfish, since he paid for it with his own money).
However, D.B. is now out in Hollywood "being a prostitute" (or screenwriting). He also drives a Jaguar, which in Holden's opinion makes him a big phony.
Holden reiterates later that D.B., along with Ring Lardner, is his favorite author.
When Holden first gets to New York, D.B. is one of the people he contemplates calling while inside the phone booth.
Holden tells us that, along with all his other siblings, D.B. is incredibly smart.
Holden heads to Ernie's in Greenwich Village since that's where he used to go with D.B. There, he runs into Lillian Simmons, a girl with "big knockers" that D.B. used to date.
It's not until well into the story that we get some background information about D.B. having been in the Army. Holden informs us that D.B. landed on D-Day and despised the Army. When he would come home on leave, he would just lie on his bed and stare at the ceiling.
D.B. told Holden that if you ever really had to shoot someone in the Army, you wouldn't even know which way to point your gun. The Army, he said, is just as full of "bastards" as the Nazis.
He also made the point to Allie (and to Holden) that to be a good war writer, you don't need to actually be in the war (Emily Dickinson is his case in point).
When Holden was younger, D.B. made him read A Farewell to Arms and The Great Gatsby. Holden wasn't really a big fan of either, and D.B. responded that he was too young to appreciate them.
While Holden was in the hospital for having broken all the windows after Allie's death, D.B. told him that one of their aunts kept talking about how peaceful Allie looked at the funeral.
At the Caulfield apartment, Phoebe is sleeping in D.B.'s room, since she likes to "spread out."
Holden asks Phoebe whether D.B. is coming home for Christmas, and she responds that he's probably staying in Hollywood to write some movie about Annapolis, starring a big-shot actor.
We leave Holden's story-within-a-novel and see him in the present, when he's seventeen and narrating. He's in a "crumby place" "not too far" from Hollywood, so D.B. has driven up with some snobby English woman to visit.
D.B. wants to know what Holden thinks about all this stuff (that is, all the "stuff" Holden just told us in the novel), but Holden's not really sure how to answer that.