 His great-grandfather, Enoch White Clark, was the founder of E. W. Clark & Co. Enoch's son Edward was Clark's paternal grandfather and brother of Clarence Howard Clark Sr. Clarence Sr.'s son Clarence Jr. served as president of the Centennial National Bank.Clark was the nephew of Edward Walter Clark Jr., commodore of the Philadelphia Corinthian Yacht Club and father of Edward III; Clarence Munroe Clark, a noted tennis player like his brother; and Percy Clark, a lawyer and noted cricketer.Percy's daughter Mary was married to Nelson Rockefeller from 1930 to 1962, before he served as Vice President of the United States.