As Duke's sons were an integral part of Duke's movie life.
Their biographies, are included in the
Pals Of The Saddle Forum.

Here are the links for further discussion:-

Sons Of The Saddle- Michael Wayne (http://www.dukewayne.com/showthread.php?t=4059)

Sons Of The Saddle- Patrick Wayne (http://www.dukewayne.com/showthread.php?t=1967)

Sons Of The Saddle- Ethan Wayne (http://www.dukewayne.com/showthread.php?t=2418)