The Gang's start in 1870s and their early robberies and finishing the fan-fict in 1887 after the 5000 Gold robbery. Obviously this is going to have your style so take any liberties.

Okay really good

I'm making a oc called jack William's it takes place 3 months after john marston's death

Nice, good luck.

Okay I'll write chapter 1 later

I think Red Dead Redemption 3 should be about the Golden years of Dutch's gang, with the beginning of the game taking place during their first robbery in 1887 (or during the winter of 86-87) and with the ending taking place during the Blackwater Massacre of 1899.