How, and to what ends, has J.D Salinger incorporated family relationships into The Catcher in the Rye?

The mental descent of Holden Caulfield in The Catcher in the Rye begins with the death of his brother Allie several years before the novel begins. To Holden, Allie maintained these qualities: he was "nicest" in the family, was more "intelligent" than Holden, and "had very red hair." When he died of Leukemia, Holden lost his mind and "broke all the goddam windows [in the garage]" with his fist, "just for the hell of it."
In the novel, Holden also clings to his 10-year-old sister Phoebe, whom he says, "[S]he knows exactly what the hell you're talking about." It's Phoebe's love for Holden that keeps him going off the rails. He wants to see her and even buys her a record. It's her threat to run away with him that knocks some sense back into Holden.
One important factor about family to consider is the absence of Holden's father. He continues to send Holden to boarding schools despite the fact that Holden seems to be failing at every turn. When Holden does return home, they are noticeably absent with Phoebe's repetition of "Daddy's going to kill you" being the only reminder of him. Holden also mentions that his father is a corporate lawyer, but Holden doesn't really want to be like him.