Elizabeth Cavendish, Duchess of Devonshire
Elizabeth Christiana Cavendish, Duchess of Devonshire( 13 May 1758 – 30 March 1824) was an English novelist and aristocrat.
She is best known as Lady Elizabeth Foster, the close friend of Georgiana Cavendish, Duchess of Devonshire.
Elizabeth supplanted the Duchess, gaining the affections of William Cavendish, 5th Duke of Devonshire, and later marrying him.
Ogawa Mataji
Viscount was a general in the early Imperial Japanese Army.
He was also the father- in- law of Field Marshal Gen Sugiyama.
Lady Caroline Lamb
Lady Caroline Lamb( née Ponsonby; 13 November 1785 – 25 January 1828), known as the Honourable Caroline Ponsonby until her father succeeded to the earldom in 1793, was an Anglo- Irish aristocrat and novelist, best known for her work" Glenarvon", a Gothic novel.
She is also known for her affair with Lord Byron in 1812.
Her husband was The Hon. William Lamb, who later became Viscount Melbourne and Prime Minister.
However, she was never the Viscountess Melbourne because she died before Melbourne succeeded to the peerage.
She was the only daughter of Frederick Ponsonby, 3rd Earl of Bessborough, an Anglo- Irish peer, and Henrietta, Countess of Bessborough, and related to other leading society ladies, being the niece of Georgiana Cavendish, Duchess of Devonshire, and cousin( by marriage) of Annabella, Lady Byron.
Lady Dorothy Macmillan
Lady Dorothy Evelyn Macmillan( 28 July 1900 – 21 May 1966) was the third daughter of Victor Cavendish, 9th Duke of Devonshire, and Evelyn Cavendish, Duchess of Devonshire.
She was married to British Prime Minister Harold Macmillan from 1920 until her death.
Deborah Cavendish, Duchess of Devonshire
Deborah Vivien Cavendish, Duchess of Devonshire,( born Deborah Vivien Freeman- Mitford and latterly Deborah, Dowager Duchess of Devonshire; 31 March 1920 – 24 September 2014) was an English aristocrat, writer, memoirist and socialite.
She was the youngest and last surviving of the six Mitford sisters, who were prominent members of English society in the 1930s and 1940s.
William Cavendish, 5th Duke of Devonshire
William Cavendish, 5th Duke of Devonshire, (14 December 1748 – 29 July 1811), was a British nobleman, aristocrat, and politician.
He was the eldest son of William Cavendish, 4th Duke of Devonshire, by his wife, the heiress Lady Charlotte Boyle, "suo jure" Baroness Clifford, who brought in considerable money and estates to the Cavendish family.
He was invited to join the Cabinet on three occasions, but declined each offer.
He was Lord High Treasurer of Ireland and Governor of Cork, and Lord Lieutenant of Derbyshire.
The 5th Duke is best known for his first wife Georgiana, Duchess of Devonshire.
At the age of about twenty, Devonshire toured Italy with William Fitzherbert which is where they commissioned the pair of portraits by Pompeo Batoni.
Samuel Slack
Samuel Slack( 1757— 1822), sometimes known as" The Tideswell Vocalist", was a noted bass singer, a native of the Derbyshire Peak District and protégé of Georgiana Cavendish, Duchess of Devonshire.
Slack was a natural bass, and though of unpolished manners( in one account" an uncouth example of common manhood") he was able, thanks to the Duchess's patronage, to study under Reginald Spofforth.
At the height of his career he was the most popular bass singer in England, and he is said to have performed before King George III.
His tomb in Tideswell churchyard, initially erected by public subscription, was restored in 1891.
Georgiana Cavendish, Duchess of Devonshire
Georgiana Cavendish, Duchess of Devonshire ("née" Spencer; ; 7 June 1757 – 30 March 1806), was an English socialite, political organizer, style icon, author, and activist.
Of noble birth from the Spencer family, married into the Cavendish family, she was the first wife of William Cavendish, 5th Duke of Devonshire, and the mother of the 6th Duke of Devonshire.
As the Duchess of Devonshire, she garnered much attention and fame in society during her lifetime.
With a pre-eminent position in the peerage of England, the duchess was famous for her charisma, political influence, beauty, unusual marital arrangement, love affairs, socializing, and gambling.
She was the great-great-great-grandaunt of Diana, Princess of Wales.
Their lives, centuries apart, have been compared in tragedy.
Louisa Cavendish, Duchess of Devonshire
Louisa Frederica Augusta Cavendish, Duchess of Devonshire, formerly Louisa Montagu, Duchess of Manchester, née Luise Fredericke Auguste, Countess von Alten( 15 June 1832 – 15 July 1911) was a German- born British aristocrat sometimes referred to as the" Double Duchess" due to her marriages to first the Duke of Manchester and later to the Duke of Devonshire.
Catherine Cavendish, Duchess of Devonshire
Catherine Cavendish, Duchess of Devonshire( 1700 – 8 May 1777), formerly Catherine Hoskins( or Hoskyn), was the wife of William Cavendish, 3rd Duke of Devonshire, and mother of the 4th Duke.

Question: Who is Georgiana Cavendish, Duchess Of Devonshire's father-in-law?
Answer: William Cavendish, 4th Duke of Devonshire