One of those lovely family groups

Marlene A Eilers Koenig collection

This group photo was taken in 1961 or 1962 -

Back row: Duke Christian Ludwig of Mecklenburg and his wife, Barbara (nee Princess of Prussia) and Hereditary Grand Duke Friedrich Franz and his wife Karin
Middle row: Duchess Thyra of Mecklenburg, Princess Elisabeth of Ysenburg-Büdingen (nee Princess of Schleswig-Holstein), Grand Duchess Alexandra of Mecklenburg (nee Hannover), Princess Irene of Schleswig-Holstein, Princess Anastasia of Schleswig Holstein (nee Duchess of Mecklenburg) and Princess Margarethe of Schleswig-Holstein
Front row: Duchess Donata of Mecklenburg, Duchess Edwina of Mecklenburg, Princess Sibylla of Schleswig-Holstein and Prince Friedrich Ferdinand of Schleswig-Holstein.

The Grand Duchess of Mecklenburg was one of 38 German royals who were to be rescued by Great Britain in the advent of a Soviet invasion of West Germany. The plans and the list of the 38 royals, prepared by the Foreign Office, were made public.
The list included Prince Philip's surviving sisters, Margarita, the Dowager Princess of Hohenlohe-Langenburg and her children, Theodora, the Margravine of Baden, and her husband and Prince and Princess Georg Wilhelm of Hanover (Sophie) and their children.
Others on the list included the elderly Dowager Duchess of Brunswick-Lüneburg, her son, the Prince of Hanover, his wife, and their six children, and her youngest son, Prince Welf, and his wife Alexandra.

At first glance, some may wonder why these royals were on a protected list. The Hanovers were also British royals, even though in 1917, the family lost their British titles when George V announced the new family name of Windsor, and limited the HRH and the title of Prince and Princess to the children of the sovereign and the grandchildren of the sovereign in the male line (and the Prince of Wales's eldest son's eldest son.) In 1931, the Duke of Brunswick issued a non-binding decree, stating that his male line would continue to use the British titles due to being the only direct male line descended from George III. Members of the Hanover royal family continue to use the older British title: prince or princess of the United Kingdom of Great Britain and Ireland. Most members of the family also continue to seek permission to marry, according to the Royal Marriages Act. In 1956, the present Prince of Hanover's father won a court case that established his right of British citizenship (and the citizenship of about 400 others) due to the Sophia Nationality Act.
Prince Georg Wilhelm did not seek permission to marry when he wed Princess Sophie of Greece and Denmark due to his marriage taking place in 1946, one year after the war had ended. The British King was not interested in hearing from a distant cousin who had fought for Germany.
The Count of Toerring-Jettenbach and Prince and Princess Ludwig of Hesse and By Rhine were also on the list. The Count was the widower of Princess Elisabeth of Greece and Denmark, the sister of Princess Marina, Duchess of Kent. Prince Ludwig and his British-born wife, Margaret were much loved by the British royal family.

 Prince Ludwig's late brother was married to the Duke of Edinburgh's sister, Cecilie.

The Duchess of Mecklenburg was born Princess Alexandra of Cumberland, as well as a Princess of Hanover. The Duchess of Brunswick-Lüneburg was her sister-in-law. She was born Princess Viktoria Luise of Prussia, the only daughter of Kaiser Wilhelm II. In May 1913, she married Prince Ernst August of Hanover, Duke of Brunswick-Lüneburg. Their wedding was the last grand royal occasion before the outbreak of World War I. Viktoria Luise's wedding was also the final meeting between three cousins: Kaiser Wilhelm II, George V, and Nicholas II of Russia.

http://www.telegraph.co.uk/news/uknews/1517842/How-Britain-planned-to-rescue-royal-relatives.html