Ernest Augustus, Duke of Brunswick
Ernest Augustus III , reigning Duke of Brunswick , was a grandson of George V of Hanover, whom the Prussians deposed in 1866.
Prince Ernest Augustus of Hanover, Prince of Great Britain and Ireland, styled Prince Ernest of Cumberland, was born at Penzing near Vienna, the sixth and youngest child of Crown Prince Ernest Augustus of Hanover and his wife, Princess Thyra of Denmark. His father succeeded as pretender to the Hanoverian throne and as Duke of Cumberland and Teviotdale in the peerage of Great Britain in 1878. The younger Prince Ernest August became heir apparent to the dukedom of Cumberland and to the Hanoverian claim upon the deaths of his two elder brothers, George and Christian. He was a first cousin of George V of the United Kingdom, Nicholas II of Russia, and Christian X of Denmark, Haakon VII of Norway, and Constantine I of Greece.
Source: Wikipedia