Holden, the main character, creates many different relationships with all the people he encountered, whether it is with friends, family, or teachers. Relationships within families are often the hardest things to maintain on good levels. Holden's older brother has a confined and busy schedule and yet is able to fit his family in it when he comes to visit at least once a week even though Holden believes that he is selfish and heartless.
Early on in the book it is made clear that Holden doesn't deal well with his brother's death. The night his brother died he slept in the garage and broke all the windows inside it. Holden and Allie hung out all the time and one time Holden denied him from coming to the park, after Allie died, he couldn't forgive himself for not allowing him to come along.
The ducks play an important role in Holden's view on change.
The fact that these creatures come and leave bothers him throughout the novel. This is showed when Holden talks to the cab driver about the ducks and when Holden goes looking for them in Central Park. Holden is intrigued that they aren't constantly there.
Holden's trouble with being able to cope with Allie's death and the fact that everything that changes around him causes problems it is easily seen that Holden doesn't deal well with change. To him, if nothing changes, there is no more disturbances which sounds great to him because if you don't have to deal with them then he will not ever become a phony person. The biggest fear Holden has is to become a "phony" like everyone else.