Question: Who was the father of the man born Rudolph Valentino Clay?

Context paragraphs:
Odessa Grady Clay: Odessa Lee Clay (née O'Grady; February 12, 1917 – August 20, 1994) was the mother of three-time World Heavyweight Champion Muhammad Ali and Rahman Ali, and the grandmother of Laila Ali.  She married Cassius Marcellus Clay, Sr. in the 1930s and worked for some time as a household domestic to help support her young children.

Valentino (1951 film): Valentino is a 1951 American drama film billed as the life story of film legend Rudolph Valentino.  Valentino was played by near lookalike actor Anthony Dexter.

Rudolph Valentino filmography: Rudolph Valentino (1895–1926) was an Italian-born actor in the era of silent films.  He emigrated to the United States in 1913 and took a string of temporary menial jobs before becoming a film extra in 1914.  He appeared in several films until 1921—many of which are now lost.  That year he got his major break when he appeared in the role of Julio in "The Four Horsemen of the Apocalypse".  According to Valentino's biographer, Noel Botham, the film was "hailed ... [as] a masterpiece and Valentino as a star"; the film grossed $4.5 million at the North American box office.

The Son of the Sheik: The Son of the Sheik is a 1926 American silent adventure/drama film directed by George Fitzmaurice and starring Rudolph Valentino and Vilma Bánky.  The film is based on the 1925 romance novel of the same name by Edith Maude Hull, and is a sequel to the 1921 hit film "The Sheik", which also stars Rudolph Valentino.  "The Son of the Sheik" is Valentino's final film and was released nearly two weeks after his death from peritonitis at the age of 31.

When Love Grows Cold: When Love Grows Cold is a lost 1926 silent film drama directed by Harry O. Hoyt, and starring Clive Brook and Natacha Rambova in her only screen starring performance.  Rambova was chiefly famous for being the wife of Rudolph Valentino.  The film was originally titled "Do Clothes Make the Woman?"  But in view of Valentino's recent divorce from Rambova, the distributor took the opportunity to bill her as 'Mrs Valentino' and changed the title to "When Love Grows Cold".  She was mortally offended and never worked in film again.

Rudolph Valentino Case: The Rudolph Valentino Case (ルドルフ・バレンチノ事件) is a 2005 decision of the Supreme Court of Japan concerning a trial for invalidation of a trademark RUDOLPH VALENTINO.

Camille (1921 film): Camille is a 1921 American silent drama film starring Alla Nazimova as Marguerite and Rudolph Valentino as her lover, Armand.  It is based on the play adaptation "La Dame aux Camélias" ("The Lady of the Camellias") by Alexandre Dumas, "fils", which was first published in French as a novel in 1848 and as a play in 1852.  "Camille" is one of numerous screen adaptations of Dumas, "fils"' story.  The film was set in 1920s Paris, whereas the original version took place in Paris in the 1840s.  It had lavish Art Deco sets and Rudolph Valentino later married the film's art director, Natacha Rambova.

Rahman Ali: Rahman Ali (born Rudolph Valentino Clay ; July 18, 1943) is an American former heavyweight boxer.  He is the younger brother of the late Muhammad Ali.

Stolen Moments (film): Stolen Moments (1920) is a silent film starring Marguerite Namara with Rudolph Valentino playing a villain, the last film in which he played one.  It was released in December 1920, just a few months before Valentino was elevated to stardom by his performance in "The Four Horsemen of the Apocalypse" (released 6 March 1921).  In fact, filming of "Stolen Moments" was expedited so that Valentino could make it to Hollywood before filming began on "The Four Horsemen of the Apocalypse".

Valentino (1977 film): Valentino is a 1977 American biographical film directed by Ken Russell and starring Rudolf Nureyev as Rudolph Valentino.  The film is very loosely based on the life of Valentino as recounted in the book "Valentino, an Intimate Exposé of the Sheik", written by Chaw Mank and Brad Steiger.  The film also stars Michelle Phillips, Leslie Caron, and Carol Kane.

Supporting paragraphs: Odessa Grady Clay Rahman Ali
Answer: Cassius Marcellus Clay, Sr.