https://www.gamespot.com/articles/red-dead-redemption-2-brings-back-an-unexpected-ch/1100-6461056/

The Red Dead Redemption 2 gameplay trailer shed a lot more light on just how Arthur Morgan and his gang of outlaws will operate in the upcoming action game, but it also revealed some story threads as well. We know that, as a prequel, this tells the story of Dutch's gang, where the first game's protagonist, John Marston, made his outlaw name. However, the new trailer reveals that his family is along for the ride too.

In a pair of blink-and-you'll-miss-it cameos, we see both Abigail Marston and her son, Jack. Both of them are sitting at a campfire as the gang gathers around. In a separate scene, Abigail talks to Morgan one-on-one, and the mini-map at one point shows an "A" icon--possibly for Abigail. It seems the whole Marston family will factor into this story.