Princess Alexandrine of Prussia (1803–1892)
Princess Alexandrine of Prussia (23 February 1803 – 21 April 1892) was Grand Duchess of Mecklenburg-Schwerin by marriage to Paul Frederick, Grand Duke of Mecklenburg-Schwerin.
She was the daughter of Frederick William III of Prussia and Louise of Mecklenburg-Strelitz.
Duke William of Mecklenburg-Schwerin
Willem of Mecklenburg-Schwerin (Ludwigsburg, 5 March 1827 - Heidelberg, 28 July 1879), was the second son of Hereditary Grand Duke Paul Friedrich of Mecklenburg and his wife Princess Alexandrine of Prussia, daughter of Frederick William III.
Albert Visetti
Albert Anthony Visetti( 13 May 1846–10 July 1928) was a Dalmatian musician who moved to London where he was Professor of Singing at the Royal College of Music, becoming a Fellow in 1921.
He was the stepfather of the novelist Radclyffe Hall.
Gerald Rudolff Ford
Gerald Rudolff Ford( December 9, 1890 – January 26, 1962) was an American businessman, creator of Ford Industries, and Republican politician who was the stepfather of U.S. President Gerald Ford and for whom Ford legally changed his name.
John VI, Duke of Mecklenburg
John VI, Duke of Mecklenburg( 1439 – 1474) was a Duke of Mecklenburg.
Héctor Barrantes
Héctor Barrantes Sansoni( 1939–1990) was an Argentine polo player.
He was the stepfather of Sarah, Duchess of York.
Duchess Gustave Caroline of Mecklenburg-Strelitz
Duchess Gustave Caroline of Mecklenburg- Strelitz( 12 July 1694 – 13 April 1748) was a daughter of Adolphus Frederick II, Duke of Mecklenburg and Princess Maria of Mecklenburg.
Morris Harvey
Morris Harvey( 1877– 1944) was a British actor and writer.
A renowned character actor, he also wrote for the stage, including material for Broadway revues, in which he also appeared.
He was the stepfather of film director Anthony Harvey.
Jerrold Wexler
Jerrold Wexler( June 27, 1924 – November 10, 1992) was a noted American businessman and film producer.
He was the brother of cinematographer Haskell Wexler and the stepfather of actress Daryl Hannah.
Albert E. Austin
Albert Elmer Austin( November 15, 1877 – January 26, 1942) was a Republican member of the United States House of Representatives from 1939 to 1941 and member of the Connecticut House of Representatives from 1917 to 1919 and from 1921 to 1923.
He was the stepfather of Clare Boothe Luce.

Question: Who is the father of Duke William Of Mecklenburg-Schwerin?
Answer: Paul Frederick, Grand Duke of Mecklenburg-Schwerin