Born as Arthur John Stainer, he was the younger son of Ferdinand (Frank) Steiner and Lilian Blumberg. His brother was the film actor Leslie Howard and his sister, the casting director Irene Howard. His uncle was the film director Wilfrid Noy. He married the actress Jean Compton Mackenzie (a daughter of the actor Frank Compton) in 1936 and they had a son together, the stage actor Alan Howard.
^"Actor Fined £25 For Importuning". The Times (London). 3 June 1961. p. 6. "Howard,... had spent a week in Brixton Prison after pleading guilty to a charge of persistently importuning for immoral purposes, was also fined £25."