What do we learn about the Holden's brother D.B. in The Catcher in the Rye?

At the beginning of the story, Holden is in California retelling the story that landed him in a mental hospital. His older brother D.B. also lives in California working as a successful screenwriter. Like a good big brother, he visits Holden every weekend and says he will drive him home to New York in his Jaguar when the time comes. Before D.B. could afford Jags, he wrote a short story called The Secret Goldfish which...

At the beginning of the story, Holden is in California retelling the story that landed him in a mental hospital. His older brother D.B. also lives in California working as a successful screenwriter. Like a good big brother, he visits Holden every weekend and says he will drive him home to New York in his Jaguar when the time comes. Before D.B. could afford Jags, he wrote a short story called The Secret Goldfish which Holden really likes (1). He's so upset that D.B. went to Hollywood to write for movies because Holden hates movies; so, he calls his brother a prostitute for selling himself short rather than becoming a real author. 

Holden isn't the only one to think that D.B. is selling his talent out to the wrong industry. One of Holden's former English teachers from Elkton Hills also disagrees with D.B.'s choice to move to California and called him up to tell him so before he left. Holden says, "Mr. Antolini said that anybody that could write like D.B. had no business going out to Hollywood. That's exactly what I said, practically" (181).

At one point, Holden dreams of living in a cabin and inviting his family over for visits. He would have the following rules, though:

"I'd let old Phoebe come out to visit me in the summertime and on Christmas vacation and Easter vacation. And I'd let D.B. come out and visit me for a while if he wanted a nice, quiet place for his writing, but he couldn't write any movies in my cabin, only stories and books. I'd have this rule that nobody could do anything phone when they visited me. If anybody tried to do anything phony, they couldn't stay" (205).

Here again we see Holden mention D.B. being in his life, but not if he's doing anything with movies. It's a bit funny, actually. Holden isn't as close with D.B. obviously, as he was with his little brother Allie who died of Leukemia, but he doesn't completely forget about him, either.