Kaiser Wilhelm and his wife both supported the Nazis party in the early 30's hoping (Like some old-school conservatives) that the Nazis would reinstate the monarchy. When he realized the Nazis would not do so he started to criticize the Nazis. He critiqued the Jewish programs being put in place and was appalled by Kristallnacht, referring to it as "Gangsterism". When the Nazis invaded Poland he wrote to Hitler stating the house of Hohenzollern was loyal to the cause. When the Netherlands surrendered (Which is were he was in exile) he wrote to Hitler congratulating him and hoping he would reinstate the monarchy completely. Soon after this he retired from public life and was to die a year later in 1941 before Operation Barbarossa (Invasion of the Soviet Union).

Balfour, Michael (1964), The Kaiser and his Times, Houghton Mifflin

Additional question, how did they deal with the Hapsburg family in Austria? I have read before that some of the hapsburgs opposed the annexation of Austria, and would like to know a bit more