Question: Which son of Sophia of Hanover ruled part of the Holy Roman Empire?

Context articles: Karl Anselm, 4th Prince of Thurn and Taxis
Duchy of Württemberg
George I of Great Britain
Schönborn family
List of monarchs of Prussia
Heil dir, Hannover
Imperial Military Constitution
Uniformity policy
Sophia of Hanover
Joachim Whaley

Karl Anselm, 4th Prince of Thurn and Taxis, full German name: "Karl Anselm Fürst von Thurn und Taxis" (2 June 1733, Frankfurt am Main, Free Imperial City of Frankfurt, Holy Roman Empire – 13 November 1805, Winzer bei Regensburg, Electorate of Bavaria, Holy Roman Empire) was the fourth Prince of Thurn and Taxis, Postmaster General of the Imperial Reichspost, and Head of the Princely House of Thurn and Taxis from 17 March 1773 until his death on 13 November 1805.
 Karl Anselm served as "Prinzipalkommissar" at the Perpetual Imperial Diet in Regensburg for Joseph II, Holy Roman Emperor and Francis II, Holy Roman Emperor from 1773 to 1797.
The Duchy of Württemberg (German: "Herzogtum Württemberg" ) was a duchy located in the south-western part of the Holy Roman Empire.
 It was a member of the Holy Roman Empire from 1495 to 1806.
 The dukedom's long survival for nearly four centuries was mainly due to its size, being larger than its immediate neighbors.
 During the Protestant Reformation, Württemberg faced great pressure from the Holy Roman Empire to remain a member.
 Württemberg resisted repeated French invasions in the 17th and 18th centuries.
 Württemberg was directly in the path of French and Austrian armies who were engaged in the long rivalry between the House of Bourbon and the House of Habsburg.
 In 1803, Napoleon raised the duchy to be the Electorate of Württemberg of the Holy Roman Empire, and when he abolished the Empire in 1806, the Electorate was elevated as the Kingdom of Württemberg.
George I (George Louis; German: "Georg Ludwig" ; 28 May 1660 – 11 June 1727) was King of Great Britain and Ireland from 1 August 1714 until his death, and ruler of the Duchy and Electorate of Brunswick-Lüneburg (Hanover) in the Holy Roman Empire from 1698.
Schönborn is a noble and mediatised former sovereign princely family from the former Holy Roman Empire.
 Several members of the family have held high offices of the Roman Catholic Church and the Holy Roman Empire over the course of centuries, including as Bishops, Prince-Bishops, Cardinals and Prince-Electors.
 In addition to several family members having been elected monarchs of ecclesiastical principalities—the Electorate of Mainz, the Prince-Bishopric of Würzburg, the Prince-Bishopric of Worms, the Prince-Bishopric of Speyer, the Electorate of Trier, and the Prince-Bishopric of Bamberg—the family possessed a fiefdom in Franconia that held imperial immediacy, and was thus a principality of the Holy Roman Empire, the state of Schönborn.
The monarchs of Prussia were members of the House of Hohenzollern who were the hereditary rulers of the former German state of Prussia from its founding in 1525 as the Duchy of Prussia.
 The Duchy had evolved out of the Teutonic Order, a Roman Catholic crusader state and theocracy located along the eastern coast of the Baltic Sea.
 The Teutonic Knights were under the leadership of a Grand Master, the last of whom, Albert, converted to Protestantism and secularized the lands, which then became the Duchy of Prussia.
 The Duchy was initially a vassal of the Kingdom of Poland, as a result of the terms of the Prussian Homage whereby Albert was granted the Duchy as part of the terms of peace following the Prussian War.
 When the main line of Prussian Hohenzollerns died out in 1618, the Duchy passed to a different branch of the family, who also reigned as Electors of Brandenburg in the Holy Roman Empire.
 While still nominally two different territories, Prussia under the suzerainty of Poland and Brandenburg under the suzerainty of the Holy Roman Empire, the two states are known together historiographically as Brandenburg-Prussia.
 Following the Second Northern War, a series of treaties freed the Duchy of Prussia from any vassalage to any other state, making it a fully sovereign Duchy in its own right.
 This complex situation (where the Hohenzollern ruler of the independent Duchy of Prussia was also a subject of the Holy Roman Emperor as Elector of Brandenburg) laid the eventual groundwork for the establishment of the Kingdom of Prussia in 1701.
 For diplomatic reasons, the rulers of the state were known as the King in Prussia from 1701 to 1772; largely because they still owed fealty to the Emperor as Electors of Brandenburg, the "King in Prussia" title (as opposed to "King of Prussia") avoided offending the Emperor.
 As the Prussian state grew through several wars and diplomatic moves throughout the 18th century, it became apparent that Prussia had become a Great Power that did not need to submit meekly to the Holy Roman Empire.
 By 1772, the pretense was dropped, and the style "King of Prussia" was adopted.
 Thus it remained until 1871, when in the aftermath of the Franco-Prussian War, the King of Prussia Wilhelm I was crowned German Emperor.
 From that point forward, though the Kingdom of Prussia retained its status as a constituent state of the German Empire, all remaining Kings of Prussia also served as German Emperor, and that title took precedence.
Heil dir, Hannover (English: Hail to thee, Hanover), was the national anthem of the Electorate, and later Kingdom of Hanover, adopted in the early 18th century.
 Like other many rulers in the 17th & 18th century, George I of Hanover and Great Britain instructed George Handel to create an anthem.
 Handel's melody remained the United Kingdom of Great Britain and Ireland's anthem after the end of the personal union in 1837.
 Also many other German states made this melody their anthem.
 For example, it was used in the Grand Duchy of Oldenburg and the Kingdoms of Bavaria and Prussia.
 After 1871, it became the anthem of the German Empire with the lyrics "Heil dir im Siegerkranz".
 The last Holy Roman Emperor and German king, Francis II, was very impressed by Handel's theme an instructed his Court musician Haydn to create the "Kaiserhymne", which became his imperial anthem and continued to be used in the new Austrian Empire after he dissolved the Holy Roman Empire.
The Imperial Military Constitution (German: "Reichsheeresverfassung" , also called the "Reichskriegsverfassung") of the Holy Roman Empire, like the rest of the imperial constitution, grew out of various laws and governed the establishment of military forces within the Empire.
 It was the basis for the establishment of the Army of the Holy Roman Empire ("Reichsarmee"), which was under the supreme command of the Emperor but was distinct from his Imperial Troops, as it could only be deployed by the Imperial Diet.
 The last Imperial Defence Order ("Reichsdefensionalordnung"), entitled "Reichsgutachten in puncto securitatis", of 13/23 May 1681, completed the military constitution of the Holy Roman Empire.
The uniformity policy was the concept of implementing Swedish law to the dominions of Sweden during the latter's time as an empire.
 It is symbolized by the slogan unus rex, una lex et grex unus ("one king, one law, one people") possibly coined by Johan Skytte, governor-general in Swedish Estonia, Ingria and Livonia.
 However, the phrase is also found in the debates on the possible union of Scotland and England in 1607, when Sir Edwyn Sandys noted King James VI & I's view that for a perfect union there should be unus rex, unus grex, una lex.
 Most notably, the uniformity policy aimed at abolishing serfdom then common in Estonia, Livonia and the Swedish dominons in the Holy Roman Empire (Ingermanland naturally had a free peasantry).
 While implemented in Livonia against the will of the local Baltic German nobles, the Estonian and Pomeranian peasants remained serfs: Estonia had voluntarily submitted to Sweden and thus had been given leeway in keeping the traditional local law code, while Swedish Pomerania had retained its traditional law code when, on behalf of the then ruling Swedish high nobility, the Peace of Westphalia granted it to Sweden while remaining part of the Holy Roman Empire, and not in a formal cession which would have resulted in the implementation of Swedish law.
 Swedish law was thus only introduced to Swedish Pomerania after the dissolution of the Holy Roman Empire in 1806.
Sophia of the Palatinate (commonly referred to as Sophia of Hanover; 14 October 1630 – 8 June 1714) was the Electress of Hanover from 1692 to 1698.
 As a granddaughter of James VI and I, she became heir presumptive to the crowns of the Kingdom of England and the Kingdom of Ireland under the Act of Settlement 1701.
 After the Acts of Union 1707, she became heir presumptive to the unified throne of the Kingdom of Great Britain.
 She died less than two months before she would have become queen, and her claim to the throne passed on to her eldest son, George Louis, Elector of Hanover, who ascended as George I on 1 August 1714 (Old Style).
Joachim Whaley (born September 1954 near London) is a historian and linguist at Cambridge University where he is Professor of German History and Thought.
 He is also a Fellow of Gonville and Caius College.
 He teaches and researches in German history and culture since 1500 and contemporary German politics.
 He also teaches German language and has a special interest in translation.
 He has 27 works in 102 publications in two languages (English and German) and his "Mirrors of mortality: studies in the social history of death" has 24 English editions published between 1981 and 2012.
 He is the author of "Religious Toleration and Social Change in Hamburg, 1529-1819 "(Cambridge, 1985) and of "Germany and the Holy Roman Empire 1493-1806," (Oxford, 2012) a study of the Holy Roman Empire published in two volumes.
 His books on toleration and on the Holy Roman Empire have been translated into German.
 He has also written numerous articles, reviews and contributed to handbooks and lexicons of German history and literature.
 In 2010 he was awarded a Pilkington Teaching Prize by the University of Cambridge.
 Joachim Whaley has been a Fellow of the Royal Historical Society since 1984.
 In 2013 he was awarded a LittD by the University of Cambridge for his books and articles on early modern German history.
 He was elected Fellow of the British Academy in July 2015.