King George VI, Queen Elizabeth (the Queen Mother), Princess Margaret Rose, and Princess Elizabeth (future Queen Elizabeth II). Love this picture for Queen Elizabeth I and Princess Elizabeth(Queen Elizabeth II).
Tsar Nicholas II of Russia and King George V of Great Britain. Maternal first cousins through their mothers, Princesses Alix (Queen Alexandra) and Dagmar of Denmark (Tsarina Maria Feodorovna). I believe the German Kaiser Wilhelm was also a relative.