Cecilie of Mecklenburg-Schwerin, Crown Princess of Germany and Prussia (1886 - 1954) in a full-length dress, 1908. (Photo by Estate of Emil Bieber/Klaus Niermann/Getty Images)

Cecilie of Mecklenburg-Schwerin, Crown Princess of Germany and Prussia (1886 - 1954) in a full-length dress, 1908. (Photo by Estate of Emil Bieber/Klaus Niermann/Getty Images)

Cecilie of Mecklenburg-Schwerin, Crown Princess of Germany and Prussia (1886 - 1954), circa 1915. (Photo by Estate of Emil Bieber/Klaus Niermann/Getty Images)

Cecilie of Mecklenburg-Schwerin, Crown Princess of Germany and Prussia (1886 - 1954), circa 1915. (Photo by Estate of Emil Bieber/Klaus Niermann/Getty Images)

Cecilie of Mecklenburg-Schwerin, Crown Princess of Germany and Prussia (1886 - 1954) with her first son, Prince Wilhelm (1906 - 1940), 1908. (Photo by Estate of Emil Bieber/Klaus Niermann/Getty Images)

Cecilie of Mecklenburg-Schwerin, Crown Princess of Germany and Prussia (1886 - 1954) with her first son, Prince Wilhelm (1906 - 1940), 1908. (Photo by Estate of Emil Bieber/Klaus Niermann/Getty Images)

Crown Prince Friedrich Wilhelm of Germany and Prussia (1882 - 1951), with his wife, Duchess Cecilie of Mecklenburg-Schwerin (1886 - 1954) in the year they were married, 1905. (Photo by Estate of Emil Bieber/Klaus Niermann/Getty Images)

Crown Prince Friedrich Wilhelm of Germany and Prussia (1882 - 1951), with his wife, Duchess Cecilie of Mecklenburg-Schwerin (1886 - 1954) in the year they were married, 1905. (Photo by Estate of Emil Bieber/Klaus Niermann/Getty Images)

Cecilie of Mecklenburg-Schwerin, Crown Princess of Germany and Prussia (1886-1954), 1912. (Photo by Estate of Emil Bieber/Klaus Niermann/Getty Images)

Cecilie of Mecklenburg-Schwerin, Crown Princess of Germany and Prussia (1886-1954), 1912. (Photo by Estate of Emil Bieber/Klaus Niermann/Getty Images)