J. R. Ackerley
Joe Randolph "J. R." Ackerley (4 November 1896 – 4 June 1967) was a British writer and editor.
Starting with the BBC the year after its founding in 1927, he was promoted to literary editor of "The Listener," its weekly magazine, where he served for more than two decades.
He published many emerging poets and writers who became influential in Great Britain.
He was openly homosexual, a rarity in his time when homosexual activity was forbidden by law and socially ostracized.
Ackerley's extramarital half-sister was Sally Grosvenor, Duchess of Westminster.
Hypatius (consul 359)
Flavius Hypatius( c. 340- died after AD 383) was a Roman Senator, who was the brother- in- law of the Roman emperor Constantius II.
Greg Penner
Gregory B. Penner( born December 18, 1969) is an American businessman and venture capitalist.
Penner was named the chairman of Walmart on June 5, 2015.
He is the son-in- law of S. Robson Walton and the grandson- in- law of Sam Walton, the founder of Walmart.
Robert W. Levering
Robert Woodrow Levering( October 3, 1914 – August 11, 1989) was a U.S. Representative from Ohio, son-in- law of Usher L. Burdick and brother- in- law of Quentin N. Burdick.
Sally Grosvenor, Duchess of Westminster
Sally Grosvenor, Duchess of Westminster ("née" Perry; 1909 – 30 May 1990), was the wife of Gerald Grosvenor, 4th Duke of Westminster.
Wyndham Goold
Wyndham Goold( 1812-1854) was a Member of Parliament( MP) for County Limerick from 1850 to 1854.
Goold was educated at Westminster School and Trinity College, Dublin.
He was the son in law of Frederick Falkiner Goold, Archdeacon of Raphoe and brother in law of Bishop Hamilton Verschoyle
Eusebius (consul 359)
Flavius Eusebius( died after AD 371) was a Roman Senator, who was the brother- in- law of the emperor Constantius II.
Nick Sidi
Nick Sidi( born 22 February 1966 in Manchester, England) is an English actor.
He is the son -in- law of actress Rosalind Knight and brother- in- law of actress Susannah Elliott- Knight.
He often plays drama or comedy roles on television and frequently appears in BBC dramas.
Charles Francis Norton
Charles Francis Norton( 1807 – 1835) was a 19th- century Member of Parliament for Guildford.
Norton was also a Captain of 52nd Light Infantry; son-in- law of Sir Colin Campbell; brother- in- law of writer Caroline Norton
Robert Vadra
Robert Vadra is an Indian businessman, entrepreneur and the husband of Priyanka Gandhi.
He is the son -in- law of Sonia Gandhi and Rajiv Gandhi, and the brother- in- law of Rahul Gandhi.

Question: Who is the sibling-in-law of J. R. Ackerley?
Answer: Gerald Grosvenor