While I wasn't able to find much, I was able to find some sources that brought some light to your question.

Earnst Hess, the Protestant son of a Jewish mother served as Corporal Hitler's commanding officer during WW1. Being the son of a Jewish mother, under Nazi Race Laws, Hess was considered a "full-blooded Jew", which would have inevitably made him a target under Hitler's oppression. However, in a letter from August 27, 1941 to the Dusseldorf Gestapo, Heinrich Himmler, one of the architects of the Final Solution, instructed the secret police to grant Hess "the relief and the protection as per the Fuhrer's wishes".

Hess's daughter Ursula, said her father had few memories of Hitler other than that he had no friends in the regiment.

Fritz Wiedemann, a former member of his unit, served as Hitler's personal adjutant from 1934 to 1939.

August Kubizek, a childhood friend of Hitler's was hired in 1938 by the Nazi Party to write two short propaganda booklets called Reminiscences about his youth with Hitler.