Stanley Livingston
The 1960-1972 series "My Three Sons," which ran first on ABC and then on CBS, is the progenitor of the single-parent sitcom genre. It also was an early indication of how a successful film star, Fred MacMurray, could transition to an more broadly popular role on the small screen, in this case as widowed dad Steve Douglas. Playing his third son, Chip, was Stanley Livingston. He is the only actor along with MacMurray to work the entire length of the series. In later years, Livingston's real-life brother Barry played his on-screen adopted sibling, Ernie. Livingston came up through the ranks via "The Adventures of Ozzie and Harriet," playing the incidental role of a small boy on half a dozen episodes. While he never crashed and burned in his adult life like many a child star, he never found his footing again in the TV or film industry. He resurfaced much later, briefly, as the director of failed 2000 series "Cory the Clown."