Friedrich Eugen, Duke of Württemberg (21 January 1732, Stuttgart – 23 December 1797, Hohenheim), the fourth son of Duke Karl Alexander, Duke of Württemberg and Princess Maria Augusta of Thurn and Taxis (11 August 1706 – 1 February 1756).
After serving with Frederick the Great during the Seven Years’ War, he took up residence in 1769 at his family’s exclave, the County of Montbéliard, of which he was also made lieutenant-general in March 1786 by his eldest brother, Charles Eugene, Duke of Württemberg, who had begun to come into the inheritance of portions of the County of Limpurg in the 1780s. He bought the castle and lordship of Hochberg in 1779, but re-sold it in 1791 to his brother. The next year he was named governor of the margraviate of Ansbach-Bayreuth by King Frederick William II of Prussia, to whom it had been sold by the last prince of that branch of the House of Hohenzollern. Montbéliard was taken over by the short-lived Rauracian Republic in 1792, then annexed by the French Republic in 1793.
His elder brothers had only daughters, so following Charles Eugene’s death in 1793 and then that of their brother Duke Ludwig Eugen (1731–1795), Frederick Eugene became reigning duke until his own death two years later. He acquiesced to the 1796 Treaty of Paris with revolutionary France in which his claims to Montbéliard (which had only been restored to Wüttemberg in 1738 by the Peace of Vienna: its attached lordships were returned by France in 1748, but under the condition of the substitution of French for Württemberger vassalage) and all other territories on the left bank of the Rhine River were renounced. Frederick Eugene thereby retained, however, France’s recognition of the integrity of the duchy of Württemberg itself.
Frederick Eugene married Friederike Sophia Dorothea of Brandenburg-Schwedt, a niece of Frederick the Great, by whom he had twelve children:
Frederick I (6 November 1754 – 30 October 1816), his successor, who would later become the first King of Württemberg;
Louis (30 August 1756 – 20 September 1817);
Eugene (21 November 1758 – 20 June 1822);
Sophie Dorothea (25 October 1759 – 5 November 1828), married to Paul I, Emperor of Russia;
William Frederick Philip (27 December 1761 – 10 August 1830); father of Wilhelm, 1st Duke of Urach;
Ferdinand Frederick Augustus (22 October 1763 – 20 January 1834), married Princess Kunigunde von Metternich, sister of Klemens Wenzel, Prince von Metternich;
Friederike Elisabeth Amalie (27 July 1765 – 24 November 1785), married to Peter I, Grand Duke of Oldenburg;
Elisabeth Wilhelmine Luise (21 April 1767 – 18 February 1790), married to Francis II, Holy Roman Emperor;
Friederike Wilhelmine Katharina (3 June 1768 – 22 October 1768);
Charles Frederick Henry (3 May 1770 – 22 August 1791);
Alexander Frederick Charles (24 April 1771 – 4 July 1833), the founder of the fifth branch of Württemberg, to which today’s head of the House, Duke Carl Maria of Württemberg, belongs;
Charles Henry (3 July 1772 – 28 July 1833), married under the name “Count von Sontheim” in 1798 Christianne-Caroline Alexeï (1779–1853), who was created Baroness von Hochberg und Rottenburg in 1807 and was raised, along with her children, to the rank and title of Countess von Urach on 12 November 1825. Of their five daughters three died young, while Countess Marie von Urach (1802–1882) wed Karl, Prince of Hohenlohe-Kirchberg in 1821 and Countess Alexandrine von Urach (1803–1884) married Charles, Count Arpeau de Gallatin in 1825, from whom she was divorced in 1843.
His daughter, Sophie Dorothea, married Emperor Paul I of Russia and became Empress Marie Feodorovna. The Empress was mother to (among others) Emperors Alexander I and Nicholas I of Russia as well as Queen Anna Paulowna of the Netherlands (from whom the current Dutch royal family is descended) and Grand Duchess Maria Pavlovna of Saxe-Weimar-Eisenach, great-grandmother of German Emperor William II.
Through his second son, Duke Louis of Württemberg, he is also ancestor of Elizabeth II of the United Kingdom and Juan Carlos I of Spain. Through his eldest son, Frederick I, he is an ancestor of Boris Johnson, elected Mayor of London in 2008 and 2012.