Forbes was born in Anoka, Nebraska, and graduated from UCLA after serving as the first editor of the Daily Bruin.
Forbes returned to Los Angeles in 1951 to assume control of the family business, the Southern California Music Co.
During the free speech movement of the 1960s, Forbes chaired a committee to examine causes behind the student unrest and ways to address it.
After the death of his first wife, Ann Fontron, Forbes married Madeleine Carpenter.
Myrna Oliver, "William E. Forbes; Businessman, UC Regent During 1960s," Los Angeles Times, August 18, 1999.