 Sinclair was the son of Arthur Hould and Amy Beatrice Hould.Sinclair was a juvenile player turned film editor who retained his celebrity in his native New Zealand long after the end of his Hollywood acting career.Sinclair's feature credits include William Wellman's "The Light That Failed," "Tower of London", Alexander Korda's "That Hamilton Woman", Raoul Walsh's "Desperate Journey", and "Thoroughbreds Don't Cry" with Mickey Rooney and Judy Garland.