Princess Nina Georgievna of Russia, (Russian: Нина Георгиевна ) (20 June 1901 – 27 February 1974), was the elder daughter of Grand Duke George Mikhailovich and Grand Duchess Maria Georgievna of Russia.
 A great-granddaughter of Tsar Nicholas I of Russia, she left her native country in 1914, before World War I finished her education in England and spent the rest of her life in exile.
 In London in 1922, she married Prince Paul Chavchavadze, a descendant of the last king of Georgia.
 They had one child, Prince David Chavchavadze, born there two years later.
 In 1927 the family of three moved to the United States and settled in New York.
 In 1939 they bought a home in Wellfleet, Massachusetts.
 Princess Nina was an artist, her husband worked as an author; he wrote five books and translated several others.
 Their son, Prince David Chavchavadze, served with the U.S. Army during World War II and, thanks in part to his knowledge of Russian, eventually became a CIA officer.
 After his retirement, he wrote his memoirs and published those of his grandmother, Grand Duchess George, as well as a book about the grand dukes of Russia.
Prince Georgy Konstantinovich of Russia (6 May 1903 – 7 November 1938), was the youngest son of Grand Duke Konstantin Konstantinovich of Russia and his wife Grand Duchess Yelizaveta Mavrikiyevna.
Grand Duchess Elena Vladimirovna of Russia (17 January 1882 – 13 March 1957), sometimes known as Helen, Helena, Helene, Ellen, Yelena, Hélène, or Eleni, was a Russian grand duchess as the only daughter and youngest child of Grand Duke Vladimir Alexandrovich of Russia and Duchess Marie of Mecklenburg-Schwerin.
 Her husband was Prince Nicholas of Greece and Denmark and they were both first cousins of Tsar Nicholas II of Russia.
Infanta Marie Anne of Portugal (Portuguese: "Maria Ana" ; 13 July 1861 – 31 July 1942) was Grand Duchess of Luxembourg as the wife of Grand Duke Guillaume IV and the country's regent in the name of their daughter, Grand Duchess Marie-Adélaïde.
 She was a member of the House of Braganza.
Grand Duchess Maria Kirillovna of Russia, (2 February 1907 – 25 October 1951) was the eldest daughter of Grand Duke Kirill Vladimirovich of Russia and Grand Duchess Victoria Feodorovna.
 She was born in Coburg when her parents were in exile because their marriage had not been approved by Tsar Nicholas II.
 She was generally called "Marie," the French version of her name, or by the Russian nickname "Masha."
 The family returned to Russia prior to World War I, but was forced to flee following the Russian Revolution of 1917.
Michelle Anches (?
 - 1926) was a woman who claimed to be the Grand Duchess Tatiana Nikolaevna of Russia.
 In 1925, Anches headed to Denmark to meet with Grand Duchess Tatiana's grandmother, Maria Feodorovna.
 But Michelle was killed in her house, so she never met her alleged grandmother.
 There are still unknown details about her death.
 Michelle Anches was considered very similar to the Grand Duchess Tatiana Nikolaevna of Russia.
Marie-Adélaïde (Marie Adelheid Thérèse Hilda Wilhelmine; 14 June 1894 – 24 January 1924), reigned as Grand Duchess of Luxembourg from 1912 until her abdication in 1919.
 She was the first Grand Duchess regnant of Luxembourg (after five grand dukes), its first female monarch since Duchess Maria Theresa (1740–1780, who was also Austrian Empress) and the first Luxembourgish monarch to be born within the territory since Count John the Blind (1296–1346).
Grand Duke Konstantin Konstantinovich of Russia (Russian: Константи́н Константи́нович ; ] ; 22 August 1858 in Strelna – 15 June 1915 in Pavlovsk) was a grandson of Emperor Nicholas I of Russia, and a poet and playwright of some renown.
 He wrote under the pen name "K.R.", initials of his given name and family name, Konstantin Romanov.
Marie Anna of Saxony, Grand Duchess of Tuscany (15 November 1799 – 24 March 1832), (full name: Maria Anna Carolina Josepha Vincentia Xaveria Nepomucena Franziska de Paula Franziska de Chantal Johanna Antonia Elisabeth Cunigunde Gertrud Leopoldina), was a princess of Saxony.
 She became Grand Duchess of Tuscany by her marriage to Leopold II, Grand Duke of Tuscany.
His or Her Grand Ducal Highness (abbreviation: HGDH) is a style of address used by the non-reigning members of some German ruling families headed by a Grand Duke.
 No currently reigning family employs the style, although it was used most recently by the younger sisters of the late Grand Duchess Charlotte of Luxembourg.
 Since Grand Duchess Charlotte's marriage to Prince Felix of Bourbon-Parma, all of their male-line descendants have used the style Royal Highness, which he bore.

Question: What was the pen name of the husband of Grand Duchess Yelizaveta Mavrikiyevna ?
Answer: "K.R."