I looked for a position avoiding the light reflection in this portrait, but I could not find any.

Many people, including myself, did not knew that Wilhelm was handicapped since birth.
His left arm was underdeveloped due to nerve damage occurred during birth. That's why
he was mostly photographed with left arm hidden behind a helmet, or a book. As a boy
he was often tied up to a scaffold "helping" to overcome the disability. With the time
he grew angry and resentful toward these "English doctors", and that was one of the
factors leading to his misjudgement of political bounds between England and Germany.