 Among their children was Queen Victoria Eugenia of Spain.In his boyhood and early youth Alexander frequently visited Saint Petersburg, and he accompanied his uncle, Tsar Alexander II, who was much attached to him, during the Bulgarian campaign of 1877.When, under the Treaty of Berlin (1878), Bulgaria became an autonomous principality under the suzerainty of the Ottoman Empire, the Tsar recommended his nephew to the Bulgarians as a candidate for the newly created throne, and the Grand National Assembly unanimously elected Prince Alexander as Prince of Bulgaria (29 April 1879).