i think i may of just gotten the German Personal union Wank happy meal!

because no one else seemed to like this POD i looked into it, turns out that none of George III brothers had any kids which lead me to the line of his older sister Princess Augusta, and her son Frederick William (he's dead by the time of the POD) his sons Charles II, Duke of Brunswick, William, Duke of Brunswick both born before the POD, so it's a Hanover, Brunswick UK Personal Union, it gets better, both Charles II and William were Childless in OTL, so from William the throne passes (by way of Princess Augusta's daughter Duchess Augusta and her son William I of Württemberg) to the king of Württemberg, Charles I, who was also born pre-POD so in 1883 the Hanover, Brunswick UK Personal Union becomes Hanover Brunswick
Württemberg UK Personal Union
so our Monarchs go as so
George IV of United Kingdom of Great Britain and Ireland and Hanover 29 January 1820 – 26 June 1830
William IV of United Kingdom of Great Britain and Ireland and Hanover 26 June 1830 – 20 June 1837
Ernest Augustus I of United Kingdom of Great Britain and Ireland and Hanover 20 June 1837 — 18 November 1851
Marry III of United Kingdom of Great Britain and Ireland 18 November 1851- 30 April 1857
William I/II/V Duke of Brunswick 9 September 1830-18 October 1884 King of Hanover 18 November 1851-18 October 1884 King United Kingdom of Great Britain and Ireland and Hanover and Brunswick 30 April 1857-18 October 1884
Charles I/IV/III King of Württemberg 25 June 1864- 6 October 1891 King United Kingdom of Great Britain and Ireland and Hanover and Brunswick 18 October 1884-6 October 1891