Found this after a Google search.
When Hitler invaded the Netherlands, the British government offered the Kaiser asylum in Britain. The Kaiser appreciated the irony of the British government’s offer (as a man accused of war crimes by the Allies after the First World War), but he refused the British government’s kind offer.
He also refused to reenter Germany, however, even despite a Nazi offer to allow him to settle into retirement anywhere he wanted in the Reich.
During the campaign in France in 1940, the Kaiser’s grandson, Prince Wilhelm, was killed in action. Hitler was very peevish about Prince Wilhelm’s death. He ordered General Baron Alexander von Falkenhausen (at the time, military commander in the Netherlands) under no circumstances to go personally to the Kaiser to break the bad news of his beloved grandson’s death. Hitler intended for Falkenhausen to send a lowly courier (a very clear attempt at a slight to the old Kaiser). Falkenhausen, however, sent the loyal monarchist General Alfred Streccius instead.
Prince Wilhelm’s funeral was attended by huge crowds in Berlin, and Hitler, even more peeved as a result, promulgated a secret protocol that all Hohenzollerns were to be expelled from the Armed Forces as soon as possible. This secret protocol affected one of the Kaiser’s sons (Major-General Prince Oskar of Prussia) and several of his grandsons (including Prince Louis Ferdinand of Prussia, Prince Georg Wilhelm of Hanover, and Prince Burkhard of Prussia), and even distant cousins (including Prince Franz Joseph of Hohenzollern-Emden).
When the German Army entered Paris, the Kaiser sent Hitler a congratulatory telegram. Some people hold that telegram against the old Kaiser, but given that he had been at the head of the German nation when it failed to defeat the French, he took pride in the victory of his Generals in 1940 (since most the commanders of Hitler’s French campaign had been trained during the First World War under the Kaiser’s command -- not by Hitler or the Nazis). The Kaiser probably sent the telegram out of sincere patriotism and pride in the truly breath-taking German victory.
When the Kaiser died in 1941, Hitler wanted his body brought back to Germany for a big funeral -- as a propaganda stunt. A codicil to the Kaiser’s will was, however, extremely clear. If he did not return to Germany as its monarch before his death, his body was to be buried at Doorn Haus in exile -- and, the Kaiser added (repeating it three or four times in the course of the codicil) that there were to be absolutely no swastikas visible at his funeral.
Hitler was peeved once again. The Führer made a point of sending a huge flower arrangement with a big, fat swastika on it, but he didn’t attend the funeral himself, sending Dr. Arthur Seyss-Inquart as his representative instead. He refused to allow any German military officers to attend the funeral, but many did anyway -- out of uniform. The World War I Field Marshal August von Mackensen (father of World War II Colonel-General Eberhard von Mackensen and Nazi Ambassador Hans Georg von Mackensen) defied the Führer’s orders and showed up at the funeral in his Field Marshal’s uniform with his Field Marshal’s baton, and he made a real point of being seen in a prominent position in the funeral procession.
Goebbels ordered all German newspapers to note the Kaiser’s passing with a small, one-paragraph obituary on a back page. It was the Nazis’ final insult to the old Kaiser’s memory.
