His sister, Lady Mary Douglas-Hamilton, married in 1869 Albert, Prince of Monaco, but their marriage was declared invalid in 1880. She then married Count Tassilo Festetics, a Hungarian noble. The 12th duke left no male issue (both sons dying w/o issue) and was succeeded in 1895 by his kinsman, Alfred Douglas, a descendant of the 4th Duke.
Mary married twice. Her first marriage, on 21 September 1869, was to Prince Albert I of Monaco (the famous oceanographer--I saw his museum when I was in Monaco). They were divorced on 28 July 1880. They are great-grandparents of the current prince, Rainier III of Monaco (to be thought of now as he seems to be on the verge of dying). Her 2nd marriage, on 2 June 1880, was to Tassilo, Count Festetics von Tolna, an officer in the Austrian imperial guard, and their daughter, Maria Mathilde Georgine was born in 1881. They are great grandparents of Princess Virginia Carolina Theresa Pancrazia Galdina von Fürstenberg, known as Ira von Fürstenberg.
Within a year of their marriage, the couple's only child, Louis was born, but the strong-willed 19-year-old Scots girl disliked Monaco and everything about it. Shortly thereafter, she left Monaco permanently and the marriage was annulled in 1880. Through his maternal grandfather, Prince Louis was related to the British aristocracy and through his maternal grandmother to the Royal Families of Belgium and Romania.
Princess Caroline, Prince Albert's grandmother, was anxious for her grandson to make such an illustrious alliance. By Albert marrying Mary Victoria he would become, by marriage, a cousin to Emperor Louis Napoleon. Despite the fact that Lady Mary Victoria was considered to be a very lovely young woman Albert found her to be rather "empty headed". Mary Victoria, while finding Albert to be handsome, did not particularily like him. However, they were forced into marriage. They were married September 21, 1869. The couple separated months before Louis was born in July 1870. In January of 1870 Mary Victoria, no longer able to cope with morning sickness and the gloominess of the palace, decided to leave Monaco with her mother, the Dowager Duchess, for Baden-Baden. It was there that Mary gave birth to her son Prince Louis-Honore-Charles-Antoine on July 12, 1870. She and Prince Albert were never reconciled and the marriage was dissolved when he in 1880 when Louis was 10.
That same year, the former Princess of Monaco married in Florence, Italy to a Hungarian nobleman, Tassilo, Prince Festetics von Tolna, 1850-1933. They had a daughter, Maria, who would become the paternal grandmother of the fashion designer Egon von Fürstenberg and his sister Ira von Fürstenberg, a European B-movie actress, European socialite, jewelry designer, and a former public relations manager for the fashion designer Valentino Garavani who would later become a companion of her cousin Rainier III of Monaco.
Ira's first husband, whom she married at Venice, Italy, in 1955, was Alfonso, Prince zu Hohenlohe-Langenburg (who was born 1924). At the time of the wedding, the bride was 15, the groom, 31. They were divorced in 1960, and the marriage was annulled in 1969. They have two sons. The prince is the founder of the Marbella Club, a renowned Spanish resort
