Which son of Sophia of Hanover ruled part of the Holy Roman Empire?
Sophia of Hanover:  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). George I of Great Britain: 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.
George I