Holdens connection to Allie

I think Allie has had a deep affect on Holden. It's obvious from the way that Holden keeps referring to him all the time, and how he tells the story about punching out the window because Allie died. It's obvious that Holden cares for Allie a lot. I think the reason for this is a couple things. First off it's his brother so he's going to be close to him, but he's also young and not part of the "phony" adult world. Maybe Holden saw a little bit of himself in his younger brother. Maybe when Allie died Holden felt that part of himself had died along with him. Maybe Allie was one of the few connections that keep Holden in the real world. There are so many reasons that he could have felt this way, and it's practically impossible to tell if it's just one or all or a few of them. Maybe it wasn't Allie that he cared about, but the ideas that Allie represented to him?