In 1971, James Keach and Stacy Keach played brothers in The Wright Brothers (1971). This gave James the idea that they should play Jesse and Frank James in a movie together. Stacy financed James to write a country musical about the brothers, which was eventually produced in Pennsylvania and New York. The Keaches then decided to turn the musical into a feature film screenplay in which both could star. In 1974, James was acting opposite Robert Carradine in The Hatfields and the McCoys (1975) and mentioned the project to him. Carradine suggested he and his brothers play the Younger brothers. The idea that all the brothers in the story be played by real-life brothers expanded.
The roles of Jesse James and his son, little Jesse, are played by father and son, James and Kalen Keach.
Edward Bunker, who plays Chadwell in the Northfield bank robbery, was actually, among many other things, a convicted bank robber.
The film stars four sets of actual brothers: the Carradines, the Keachs, the Quaids and the Guests.
In order to make the movie, David Carradine forfeited his customary profit participation and the Keach brothers gave up their profit percentages as executive producers, so that the Carradine brothers got the same amount of profits. When the film went over its $7.5 million budget, the Keaches forfeited their executive producer fees.