Question: When was the 7th Duke of Westminster which Gerald Grosvenor was his father born 

Context paragraphs:
Gerald Grosvenor, 6th Duke of Westminster: Major General Gerald Cavendish Grosvenor, 6th Duke of Westminster, (22 December 1951 – 9 August 2016) was a British landowner, businessman, philanthropist, Territorial Army general and hereditary peer.  He was the son of Robert George Grosvenor, 5th Duke of Westminster and Viola Grosvenor.  He was Chairman of the property company Grosvenor Group.  He is succeeded by his son, Hugh Grosvenor, 7th Duke of Westminster.

Nicholas Ashley-Cooper, 12th Earl of Shaftesbury: Nicholas Edmund Anthony Ashley-Cooper, 12th Earl of Shaftesbury Bt, (born 3 June 1979) also known as Nick Ashley-Cooper, is an English peer, landowner and philanthropist.  He succeeded his brother as Earl of Shaftesbury in 2005.  The 12th Earl of Shaftesbury is the godson of Gerald Grosvenor, 6th Duke of Westminster, and Simon Elliot, brother-in-law of Charles, Prince of Wales.

La Garganta (finca): La Garganta (Spanish for "the throat", or "gully") is a private estate, or finca, of around 15,000 ha (32,000 acres) in extent, located in the rugged Sierra Morenain, in rural Ciudad Real province, Castile-La Mancha region, Spain.  It is situated between the town of Conquista and the hamlet of Minas de Horcajo, in Almodóvar del Campo.  Around 2003 it was bought on lease and renovated by Gerald Grosvenor, 6th Duke of Westminster.

Gerald Grosvenor, 4th Duke of Westminster: Colonel Gerald Hugh Grosvenor, 4th Duke of Westminster {'1': ", '2': ", '3': ", '4': "} (13 February 1907 – 25 February 1967) was the son of Captain Lord Hugh William Grosvenor and Lady Mabel Crichton and a grandson of Hugh Grosvenor, 1st Duke of Westminster.

Viola Grosvenor, Duchess of Westminster: Viola Grosvenor, Duchess of Westminster (10 June 1912 – 3 May 1987) was the wife of Robert Grosvenor, 5th Duke of Westminster.

Natalia Grosvenor, Duchess of Westminster: Natalia Ayesha Grosvenor, Duchess of Westminster ("née" Phillips; born 8 May 1959) is the widow of Gerald Grosvenor, 6th Duke of Westminster.  The Duchess will assume the style of Dowager Duchess only upon the marriage of her son.  At the time of her husband's succession to the title, there were four Duchesses of Westminster, the current Duchess, Sally Grosvenor, Duchess of Westminster, Anne Grosvenor, Duchess of Westminster and Viola Grosvenor, Duchess of Westminster.

Hugh Grosvenor, 7th Duke of Westminster: Hugh Richard Louis Grosvenor, 7th Duke of Westminster (born 29 January 1991), styled as Earl Grosvenor until August 2016, is a British aristocrat, billionaire, businessman and landowner.  He is the third child and only son of Gerald Grosvenor, 6th Duke of Westminster and his wife Natalia Phillips Grosvenor, Duchess of Westminster.  He inherited the title of Duke of Westminster on 9 August 2016, on the death of his father.  The duke is estimated to be worth US$13 billion, making him the world's richest person aged under 30.

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.

Duke of Westminster: Duke of Westminster is a title in the Peerage of the United Kingdom.  It was created by Queen Victoria in 1874 and bestowed upon Hugh Grosvenor, 3rd Marquess of Westminster.  The 2nd, 3rd, 4th and 5th Dukes were each his grandsons.  The present holder of the title is Hugh Grosvenor, who inherited the dukedom on 9 August 2016 following the death of his father, Gerald.  The present Duke is also a godfather of Prince George of Cambridge.

Westminster City Council v Duke of Westminster: Westminster City Council v Duke of Westminster was a legal case between Westminster City Council and Gerald Grosvenor, 6th Duke of Westminster heard in November 1990.  The dispute concerned 532 flats in Page Street, Vincent Street and Regency Street, Pimlico, London.  These had been designed by architect Sir Edwin Lutyens and erected between 1928-30 for Hugh Grosvenor, 2nd Duke of Westminster.  In 1937 the Duke assigned the properties - for a peppercorn rent of 1 shilling - to the council on a 999-year lease with the stipulation that they be used only as "dwellings for the working classes... and no other purpose."

Supporting paragraphs: Gerald Grosvenor, 6th Duke of Westminster Hugh Grosvenor, 7th Duke of Westminster
Answer: 29 January 1991