Vernon was born in Collins Street, Melbourne, and grew up in that city. His name was originally John Lett, and he was the son of Richard Lett, a brickmaker, and his wife Jane Catherine, née Williamson. He worked as a clerk at the age of 15 and the next year as a tea-taster and blender. He made his stage debut at the age of eighteen, at Ballarat, Victoria, in a farce, "Turn Him Out". On 2 February 1870, aged 21, as Norman Letville, he married an actress, Mary Jane Walker (d. 1905). They had nine children.