Question: This British Territorial Army general was succeeded by his son who is estimated to be worth what?

Context paragraphs:
North Irish Horse: The North Irish Horse is a yeomanry unit of the British Territorial Army raised in the northern counties of Ireland in the aftermath of the Second Boer War.  Raised and patronized by the nobility from its inception to the present day, it was one of the first non-regular units to be deployed to France and the Low Counties with the British Expeditionary Force in 1914 during World War I and fought with distinction both as mounted troops and later as a Cyclist Regiment, achieving 18 battle honours.  The regiment was reduced to a single man in the inter war years and re-raised for World War II, when it achieved its greatest distinctions in the North African and Italian campaigns.  Reduced again after the Cold War, the regiment's name still exists in B (North Irish Horse) Squadron, the Queen's Own Yeomanry and 69 (North Irish Horse) Signal Squadron (V), part of 32 Signal Regiment.

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.

John Senior: Major (Ret) John Wilson Senior, MBE, TD, mobilised on 27 December 2001, Senior was the first member of the British Territorial Army to be deployed on operational service to Afghanistan (post 11 September 2001).  He is also the founder of Heroes Welcome UK, a national scheme to encourage local communities to show their open support to British and other UK-based military personnel.

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.

167th (1st London) Brigade: The 167th (1st London) Brigade was an infantry formation of the British Territorial Army that saw active service in both the First and Second World Wars.  It was the first Territorial formation to go overseas in 1914, garrisoning Malta, and then served with the 56th (London) Infantry Division on the Western Front (World War I) and in the North African and Italian campaigns in World War II.

52nd (Lowland) Infantry Division: The 52nd (Lowland) Infantry Division was an infantry division of the British Army that was originally formed as the Lowland Division, in 1908 as part of the Territorial Force.  It later became the 52nd (Lowland) Division in 1915.  The 52nd (Lowland) Division fought in the First World War before being disbanded, with the rest of the Territorial Force, in 1920.  The Territorial Force was later reformed as the Territorial Army and the division was again raised, during the inter-war years, as the 52nd (Lowland) Infantry Division - a 1st Line Territorial Army Infantry Division - and went on to serve during the Second World War.  After the war, the division was merged with the 51st (Highland) Infantry Division in 1948.  The history of the division was carried on by the 52nd Lowland Brigade, and later the 52nd Lowland Regiment.

Regiment Boland: Regiment Boland was an infantry regiment of the South African Army.  As a reserve unit, it had a status roughly equivalent to that of a British Territorial Army or United States Army National Guard unit.

Geoffrey Woolley: Geoffrey Harold Woolley, {'1': ", '2': ", '3': ", '4': "} (14 May 1892 – 10 December 1968) was a Church of England priest, British Army officer and military chaplain.  He was the first British Territorial Army officer to be awarded the Victoria Cross, the highest and most prestigious award for gallantry in the face of the enemy that can be awarded to British and Commonwealth forces.

Tyne-Tees Regiment: The Tyne-Tees Regiment was a regiment of the British Territorial Army.  The regiment was part of 15 (North East) Brigade and was the Territorial unit of infantry in the area stretching from Scarborough in North Yorkshire, to Alnwick in Northumberland.

Gordon Williamson (writer): Gordon Williamson (born 1951) is a popular history writer based in the United Kingdom.  Williamson spent seven years with the Military Police in the British Territorial Army and, as of 2016, resides in Scotland.  Williamson has written more than 40 books and other publications.  His works have focused on topics ranging from U boats, military insignia, flying aces, the Waffen-SS, and special forces.  Williamson's works present an uncritical portrayal of the German war effort during the Second World War.

Supporting paragraphs: Gerald Grosvenor, 6th Duke of Westminster Hugh Grosvenor, 7th Duke of Westminster
Answer: US$13 billion