Holden Caulfield is the protagonist/narrator and he tells us very little about his older brother D.B. We learn that D.B. is a writer and that he writes scripts for Hollywood movies. This angers Holden because he feels that D.B. should continue to write books, and because of his brother's occupation, he refers to him as a prostitute.
"He is a successful and financially secure screenwriter in Hollywood. But Holden feels that D.B. has prostituted his art for money and should instead be writing serious works. While D.B. shows great solicitude for Holden, the relationship between the brothers is distant."
In the very beginning of the book, when Holden is in the mental hospital in California he tells us:
"He's in Hollywood. That isn't too far from this crumby place and he comes over and visits me practically every weekend. He's going to drive me home when I go home next month maybe. He just got a Jaguar. He's got a lot of dough, now. He didn't use to. He used to be just a regular writer, when he was home. He wrote this terrific book of short stories. The Secret Goldfish." (Salinger)
Holden also tells us that he hates movies, not only because his brother has given up writing serious books, but because they are all phony. Holden feels that his brother is a sellout, giving up the chance for real literary success to write scripts because of the money. Holden has a dislike for people who pursue financial success, and D.B. is the first character that Holden tells us about, characterizing him as a prostitute for working in the movie industry.
One more thing that Holden tells in a flashback was the fact that D.B. was drafted or enlisted in the Army, and went to war.
Seemingly, it caused post-traumatic syndrome on D.B. because, according to Holden, all he would do is come back to the house just to "stare at the ceiling", and maintain a persistent sadness and nostalgia.
Holden holds his negative views on the Army "a place full of bastards" precisely on how it affected D.B., whose Army experience, according to Holden also, "doesn't do a damn thing for his writing"= Perhaps this is the reason why D.B. resorted to move onto the movie science.
We learn that his brother D.B is a writer who made it big in hollywood and currently works on movies and scripts. Holden on the other hand sees this as hypocrisy and thinks his brother is selling himself cheaper than he should have. He doesn't think a job in hollywood is something to be proud of as it is mediocre to those who write well.