Princess Royal is a style customarily (but not automatically) awarded by a Britishmonarch to his or her eldest daughter. The style is held for life, so a princess cannot be given the style during the lifetime of another Princess Royal. There have been seven Princesses Royal in total [1].
Princess Victoria (1840 - 1901): daughter of Queen Victoria and Prince Albert; wife of Friedrich III, King of Prussia and German Emperor (1831 - 1888); mother of Wilhelm II, last King of Prussia and last German Emperor (1859 - 1941)