 In addition to his listing as producer, the film's opening credits indicate "song by Marlin Skiles & Charles B. Fitzsimons; sung by Maureen O'Hara" (the title of the song, which is heard through the entire length of the opening credits, is not specified).Another younger brother, Jim O'Hara (1927–1992), played the seventh-billed role of Cal (the family surname is Fitzsimons, also rendered as FitzSimons).Leading man Brian Keith was also Maureen O'Hara's co-star in "The Parent Trap" which they completed immediately before "The Deadly Companions" and which premiered on June 12, 1961, six days after the Tucson premiere of "The Deadly Companions".