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.
Viva (actress)
Viva, born as Janet Susan Mary Hoffmann( August 23, 1938), is an American actress, writer and a former Warhol superstar.
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 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.
Susan Mary Alsop
Susan Mary Alsop (June 19, 1918 – August 18, 2004) was an American socialite and writer active in Washington, D.C. political circles.
The wife of columnist Joseph Alsop and a descendant of founding father John Jay, her Georgetown home hosted dignitaries and publishers during the 1960s and 70s ranging from John F. Kennedy, Phil and Katharine Graham, and Isaiah Berlin, earning her the nickname "the grand dame of Washington society."
Mary Alsop King Waddington
Mary Alsop King Waddington( April 28, 1833 – June 30, 1923) was an American author.
She particularly wrote about her life as the wife of a French diplomat.
Eusebius (consul 359)
Flavius Eusebius( died after AD 371) was a Roman Senator, who was the brother- in- law of the emperor Constantius II.
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.
Joseph Alsop
Joseph Wright Alsop V (October 10, 1910 – August 28, 1989) was an American journalist and syndicated newspaper columnist from the 1930s through the 1970s.
He was an influential journalist and top insider in Washington from 1945 to the late 1960s, often in conjunction with his brother Stewart Alsop.
Susan Watson (academic)
Susan Mary Watson is a New Zealand law academic specialising in company law.
She is currently a full professor at the University of Auckland.

Question: Who is the sibling-in-law of Susan Mary Alsop?
Answer: Stewart Alsop