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.
Jérôme Guedj
Jérôme Guedj( born 23 January 1972 in Pantin) is a French politician.
He is a Member of the Socialist Party, member of the sixth district of Essonne, President of the General Council of Essonne, General Councillor of the Canton of Massy- Est and alderman of Massy.
Sophie Amalie Lindenov
Sophie Amalie Lindenov, Baroness of Lindenborg( 4 July 1649 – 4 August 1688) was a Danish noblewoman and landowner.
She was Baroness of Lindenborg and the owner of Lindenborg Castle.
Gisèle Pascal
Gisèle Pascal( 17 September 1921 – 2 February 2007) was a French actress and a former lover of Rainier III, Prince of Monaco.
She was born Gisèle Marie Madeleine Tallone at Cannes in France.
Her first movie role was in 1942's" L' Arlésienne".
For six years, she was involved in a relationship with Prince Rainier, and lived together in a villa in Saint- Jean- Cap- Ferrat.
Princess Antoinette, Baroness of Massy, Rainier's sister, seeking to obtain the throne of Monaco for her own son, spread malicious rumors that Pascal was incapable of bearing children.
A contemplated marriage was called off when a medical examination reported that she was infertile.
Pascal subsequently married actor Raymond Pellegrin on 8 October 1955 and had a daughter, Pascale Pellegrin, on 12 September 1962.
Princess Antoinette, Baroness of Massy
Princess Antoinette of Monaco, Baroness of Massy
(Antoinette Louise Alberte Suzanne Grimaldi; 28 December 1920 – 18 March 2011) was a member of the princely family of Monaco and the elder sister of Prince Rainier III and aunt of Albert II, Prince of Monaco.
Her parents were Count Pierre de Polignac and Princess Charlotte, Duchess of Valentinois.
She was born in Paris of French and Monegasque ancestry.
Eusebius (consul 359)
Flavius Eusebius( died after AD 371) was a Roman Senator, who was the brother- in- law of the emperor Constantius II.
Antony Armstrong-Jones, 1st Earl of Snowdon
Antony Charles Robert Armstrong- Jones, 1st Earl of Snowdon( 7 March 193013 January 2017), commonly known as Lord Snowdon, was a British photographer and filmmaker.
He was the husband of Princess Margaret and brother- in- law of Queen Elizabeth II.
Rainier III, Prince of Monaco
Rainier III (Rainier Louis Henri Maxence Bertrand Grimaldi; 31 May 1923 – 6 April 2005) was the Prince of Monaco from 1949 to his death in 2005.
Rainier ruled Monaco for almost 56 years, making him one of the longest ruling monarchs in European history.
Though internationally known for his marriage to American actress Grace Kelly, he was also responsible for reforms to Monaco's constitution and for expanding the principality's economy from its traditional casino gambling base to its current tax haven role.
Gambling accounts for only approximately three per cent of the nation's annual revenue today; when Rainier ascended the throne in 1949, it accounted for more than 95 per cent.
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.
Marie Juliette Louvet
Marie Juliette Louvet( 9 May 1867 – 24 September 1930) was the lover of the then unmarried Prince Louis II of Monaco and was the mother of his only child, Princess Charlotte of Monaco.
Known as Juliette, Louvet was the daughter of Jacques Henri Louvet( 18301910) and his first wife, Joséphine Elmire Piedefer( 18281871).
She married the photographer Achille Delmaet, but they divorced in 1893.
They had two children, Georges and Marguerite.
Juliette Delmaet became an entertainer of sorts, reportedly a cabaret singer.
In 1897, she was a hostess in a Montmartre nightclub when she met Louis through her mother, who was the prince's laundress in Paris.
She gave birth to their daughter, Charlotte, in Constantine, Algeria, in 1898.
Through her daughter she is the maternal grandmother of Rainier III, Prince of Monaco and Princess Antoinette, Baroness of Massy.

Question: Who is Princess Antoinette, Baroness Of Massy's sibling-in-law?
Answer: Grace Kelly