Of Irish descent, Kelly was born in Lowell, Massachusetts, into a theatrical family. Her mother was silent film actress Nan Kelly, who coached her and managed her career. As a child actress, Kelly appeared in 52 films made on the East Coast by the age of 17. Her younger brother was actor Jack Kelly, most noted for playing the role of Bart Maverick, one of the leads (alongside James Garner, Roger Moore or Robert Colbert) in the ABC television series Maverick (1957-1962). The Kelly siblings, who resembled each other, are not currently known to have worked together in film or television.
