Grand Duchess Alexandrine of Mecklenburg-Schwerin, born Princess of Prussia (1803-1892), and her sister-in-law, Queen Elisabeth of Prussia (1801-1873), wrote letters to each other for half a century. Elisabeth had married Alexandrine's brother, then Crown Prince Friedrich Wilhelm (IV.) Of Prussia, in 1823. The unfamiliar women became friends. As sisters in spirit, they shaped dynastic family life and defended the rule of their houses over Mecklenburg and Prussia with their own means during the revolutionary upheavals of the 19th century. The unabridged correspondence shows the varied and influential roles in which European monarchs acted: as mother, relative and confidante