Of what relation is Irina Mikhailovna Raievskya to the great-great grandson and historic heir of Wilhelm II?
Irina Mikhailovna Raievskya:  Irina is the great-grandmother of Sophie, Princess of Prussia, wife of Georg Friedrich, Prince of Prussia current head of the House of Hohenzollern. Georg Friedrich, Prince of Prussia:  He is the great-great-grandson and historic heir of Wilhelm II, the last German Emperor and King of Prussia, who was deposed and went into exile upon Germany's defeat in World War I in 1918.
great-grandmother