Question: How long has Princess Margaretha of Liechtenstein's brother reigned as Grand Duke?

full_context: Document 1: Princess Margaretha, Mrs. Ambler: Princess Margaretha, Mrs. Ambler, (Margaretha Désirée Victoria; born 31 October 1934) is a Swedish princess, the eldest sister of King Carl XVI Gustaf of Sweden and also first cousin of Queen Margrethe II of Denmark.
Document 2: Princess Margaretha of Liechtenstein: Princess Margaretha of Liechtenstein (born "Princess Margaretha of Luxembourg" on 15 May 1957) is the fourth child and second daughter of Grand Duke Jean of Luxembourg and Princess Joséphine Charlotte of Belgium. As the sister of Grand Duke Henri of Luxembourg and the sister-in-law of Prince Hans-Adam II of Liechtenstein, she is a princess of two current realms and a member of the Luxembourg and Liechtenstein reigning dynasties. The Princess holds similar precedence in both monarchies, as sister and sister-in-law of the Sovereign.
Document 3: Prince Laurent of Belgium: Prince Laurent of Belgium (French: "Laurent Benoît Baudouin Marie de Belgique", Dutch: "Laurens Benedikt Boudewijn Maria van België"; born 19 October 1963) is the second son of King Albert II and Queen Paola, and younger brother of King Philippe.
Document 4: Princess Marie of Liechtenstein (b. 1959): Princess Marie of Liechtenstein ("née" Princess Marie Isabelle Marguerite Anne Geneviève of Orléans; born Boulogne-Billancourt, France on 3 January 1959) is the eldest daughter of Prince Henri, Count of Paris, Duke of France and his former wife Duchess Marie Thérèse of Württemberg. She is the wife of Prince Gundakar of Liechtenstein, a great-grandson of Prince Alfred of Liechtenstein.
Document 5: Philippe of Belgium: Philippe (] , French: "Philippe Léopold Louis Marie" , Dutch: "Filip Leopold Lodewijk Maria" , German: "Philipp Leopold Ludwig Maria" ; born 15 April 1960) is the seventh King of the Belgians, having ascended the throne on 21 July 2013, following his father's abdication. He is the eldest child of King Albert II, whom he succeeded upon Albert's abdication for health reasons, and Queen Paola. He married Countess Mathilde d'Udekem d'Acoz (now Queen Mathilde), with whom he has four children. King Philippe's elder daughter, Princess Elisabeth, is first in the line of succession.
Document 6: Princess Amalia of Nassau: Princess Amalia of Nassau ("Amalia Gabriela Maria Teresa"; born 15 June 2014) is a Luxembourgish princess and the eldest child of Prince Félix and Princess Claire of Luxembourg. She's the first and only granddaughter and third grandchild of Grand Duke Henri. She is currently third in the line of succession, behind her paternal uncle Hereditary Grand Duke Guillaume and her father. She has a brother, Prince Liam of Nassau.
Document 7: Henri, Count of Paris (born 1933): Henri d'Orléans, Count of Paris, Duke of France ("Henri Philippe Pierre Marie d'Orléans"; born 14 June 1933), is head of the House of Orléans, and one of the current pretenders to the defunct French crown as Henry VII. A descendant in the male-line of France's "Citizen-King" Louis-Philippe d'Orléans (ruled 1830–1848), he is also recognized as the legitimate claimant to the throne by those French royalists, called Unionists, who regard him as the rightful heir of Henri de Bourbon, Count of Chambord, the last patrilineal descendant of King Louis XV. Henri of Orléans is a former military officer as well as an author and painter.
Document 8: Henri, Grand Duke of Luxembourg: Henri (Luxembourgish: "Henri Albert Gabriel Félix Marie Guillaume" , ] ; born 16 April 1955) is the current Grand Duke of Luxembourg, reigning since 7 October 2000. He is the eldest son of Grand Duke Jean and Princess Joséphine-Charlotte of Belgium, and a first cousin of Philippe, the current king of Belgium.
Document 9: Princess Nathalie of Sayn-Wittgenstein-Berleburg: Princess Nathalie of Sayn-Wittgenstein-Berleburg (Nathalie Xenia Margrethe Benedikte; born 2 May 1975, in Copenhagen, Denmark) is the youngest daughter of Prince Richard of Sayn-Wittgenstein-Berleburg and Princess Benedikte of Denmark and niece of Queen Margrethe II of Denmark and Queen Anne-Marie of Greece.
Document 10: Princess Marie Gabriele of Luxembourg: Princess Marie Gabriele of Luxembourg, Countess of Holstein-Ledreborg (given names: "Marie Gabrielle Aldegunde Wilhelmine Louise"; born 2 August 1925) is the third daughter and fourth of the six children of Grand Duchess Charlotte of Luxembourg and her husband Prince Félix. She is the younger sister of former Grand Duke Jean of Luxembourg and thus a paternal aunt to the current Grand Duke, Jean's son Grand Duke Henri. In 1951 she married Danish Count Karl Johan Ludvig, 7th Count of Holstein-Ledreborg (2 October 1919 – 25 June 2001), Roman Catholic; the couple were married for 50 years until his death in 2001. Together, they had seven daughters.
Document 11: Princess Margriet of the Netherlands: Princess Margriet of the Netherlands (Margriet Francisca; born 19 January 1943) is the third daughter of Queen Juliana and Prince Bernhard. As an aunt of the reigning monarch, King Willem-Alexander, she is a member of the Dutch Royal House and currently eighth and last in the line of succession to the throne.
Document 12: Princess Margaretha of Saxony: Princess Margaretha of Saxony, Duchess of Saxony (German: "Prinzessin Margaretha Karoline Friederike Cecilie Auguste Amalie Josephine Elisabeth Maria Johanna von Sachsen, Herzogin zu Sachsen" ) (24 May 1840 – 15 September 1858) was the eighth child and fifth eldest daughter of John of Saxony and his wife Amalie Auguste of Bavaria and a younger sister of Albert of Saxony and George of Saxony. She was born in Dresden, then in the Kingdom of Saxony. Through her marriage to Archduke Charles Louis of Austria, Margaretha was a member of the House of Habsburg-Lorraine and an Archduchess and Princess of Austria and Princess of Hungary, Croatia, Bohemia, and Tuscany.
Document 13: Prince Jean of Luxembourg: Prince Jean of Luxembourg (given names: "Jean Félix Marie Guillaume") was born on 15 May 1957 at Betzdorf Castle, the second son of Jean, Grand Duke of Luxembourg and Princess Joséphine-Charlotte of Belgium. He is the twin brother of Princess Margaretha. He frequently goes by the name of Jean Nassau.
Document 14: Princess Märtha Louise of Norway: Princess Märtha Louise of Norway (born 22 September 1971) is the only daughter and elder child of King Harald V and Queen Sonja. She is fourth in the line of succession to the Norwegian throne, after her brother Haakon, and his two children.
Document 15: Princess Margaretha of Sweden: Princess Margaretha of Sweden (Margaretha Sofia Lovisa Ingeborg; 25 June 1899 – 4 January 1977) was a member of the Swedish Royal Family and a Princess of Denmark by marriage, the eldest sister of Märtha, Crown Princess of Norway, Queen Astrid of the Belgians and Prince Carl Bernadotte.
ground_truth: since 7 October 2000.