Here is a post I did a while back on Kaiser Wilhelm II.

Wilhlem II had initially hoped that the Nazis success would lead to a restoration of the monarchy or at least rekindle interest in reestablishing it. Any hope of this ended when the last Field Marshal from the reign of the Kaiser, August von Mackensen, accepted a large amount of money and a personal estate from Hitler. Mackensen wrote the Kaiser, saying he was sorry, but Wilhelm denounced him as a traitor to the cause. Wilhelm didn't approve of the Nazis excesses, especially the infamous "night of the long knives" which he detested. Wilhelm was impressed with Nazi Germany's and Hitler's military successes though. He sent Hitler a telegram congratulating him when he conquered the Netherlands. And during the actual invasion, Wilhelm was know to sit up and mark the position of German armies on a map, tracking their progress.

Wilhelm had hosted meetings with some top Nazis like Goering, but after the Nazi takeover of the Netherlands, Hitler posted SS guards there to keep Wilhelm isolated, a number of Generals tried to see Wilhelm so they could pay their respects but they were denied entry because Hitler feared any challenge to his authority.

Source:

Third Reich in Power by Richard Evans

The Second World War by John Keegan

A World Undone by G.J Meyer.