Question: Who is the paternal grandfather of Princess Sophie Of Luxembourg?

Knowledge 1: Princess Sophie of Luxembourg
Princess Sophie Caroline Marie Wilhelmine of Luxembourg (14 February 1902 – 24 May 1941) was the sixth and youngest daughter of Grand Duke William IV and his wife, Infanta Marie Anne of Portugal. [SEP] Knowledge 2: William IV, Grand Duke of Luxembourg
William IV (William Alexander; "French:Guillaume Alexandre"; 22 April 1852 – 25 February 1912) reigned as the Grand Duke of Luxembourg from 17 November 1905 until his death.He succeeded his father, Adolphe.William was a Protestant, the religion of the House of Nassau.He married Princess Marie Anne of Portugal, believing that a Roman Catholic country ought to have a Roman Catholic monarch.Thus his heirs have been Catholic.At the death of his uncle, Prince Nikolaus-Wilhelm in 1905, the only other legitimate male in the House of Nassau-Weilburg was William's cousin, Georg Nikolaus, Count of Merenberg, the product of a morganatic marriage.So in 1907, William declared the Counts of Merenberg non-dynastic, naming his own eldest daughter Marie-Adélaïde (1894–1924) as heir presumptive to the grand ducal throne.She became Luxembourg's first reigning grand duchess upon her father's death in 1912, and upon her own abdication in 1919, was succeeded by her younger sister Charlotte (1896–1985).Charlotte's descendants reign until the present day.He was the last monarch of Luxembourg to die whilst still on the throne.
Knowledge 1: William IV, Grand Duke of Luxembourg
William IV (William Alexander; "French:Guillaume Alexandre"; 22 April 1852 – 25 February 1912) reigned as the Grand Duke of Luxembourg from 17 November 1905 until his death.He succeeded his father, Adolphe.William was a Protestant, the religion of the House of Nassau.He married Princess Marie Anne of Portugal, believing that a Roman Catholic country ought to have a Roman Catholic monarch.Thus his heirs have been Catholic.At the death of his uncle, Prince Nikolaus-Wilhelm in 1905, the only other legitimate male in the House of Nassau-Weilburg was William's cousin, Georg Nikolaus, Count of Merenberg, the product of a morganatic marriage.So in 1907, William declared the Counts of Merenberg non-dynastic, naming his own eldest daughter Marie-Adélaïde (1894–1924) as heir presumptive to the grand ducal throne.She became Luxembourg's first reigning grand duchess upon her father's death in 1912, and upon her own abdication in 1919, was succeeded by her younger sister Charlotte (1896–1985).Charlotte's descendants reign until the present day.He was the last monarch of Luxembourg to die whilst still on the throne. [SEP] Knowledge 2: Princess Sophie of Sweden
Princess Sophie of Sweden(Sofia Vilhelmina Katarina Maria Lovisa Charlotta Anna; 21 May 1801 – 6 July 1865) was, by marriage, Grand Duchess of Baden as the wife of sovereign Grand Duke of Baden, Leopold.
Knowledge 1: Princess Sophie of Sweden
Princess Sophie of Sweden(Sofia Vilhelmina Katarina Maria Lovisa Charlotta Anna; 21 May 1801 – 6 July 1865) was, by marriage, Grand Duchess of Baden as the wife of sovereign Grand Duke of Baden, Leopold. [SEP] Knowledge 2: Princess Sophie of Romania
Princess Sophie of Romania( born 29 October 1957) is the fourth daughter of King Michael I and Queen Anne of Romania.

Answer: Adolphe