Events of Red Dead Redemption 2
Duncan is first seen after his father sends John to help him ride Jeremiah, a horse which is far too big for him. John takes the horse for a ride in order to tire it out, which allows Duncan to mount it. John briefly supervises him as he rides it around the corral, before Duncan's mother tells John that she needs his help to birth a foal.
Much later on, Duncan is seen accompanying Angus in delivering some of the family's furniture to the Marstons' ranch at Beecher's Hope. Duncan and Angus unload the furniture from the wagon, and thank John for his role in saving Pronghorn Ranch.
- Red Dead Redemption 2