The American Office of Strategic Services (the predecessor of the CIA) wrote out a psychological profile of Hitler that came out (I think) in 1943 or 44. It's a fascinating read overall, and it includes a good bit about his childhood.(http://www.nizkor.org/hweb/people/h/hitler-adolf/oss-papers/text/profile-index.html) Most of the stuff about his childhood is in the "As He Knows Himself" Section.

The TL;DR of it is that Hitler was a basically intelligent but incredibly lazy child, making him a lousy student. His father was abusive to he and his siblings. He tried to keep his family history at arms length for most of his life, mostly because few of his relatives ever really made anything of themselves (or came from anything, for that matter).