Isaac was the son of Arthur and Eliza. Following a sexual encounter, Arthur learned that he got Eliza pregnant and offered help in any way he could. As Eliza took to raising Isaac upon his birth, Arthur would occasionally visit Eliza and Isaac every few months and stay with them for days at a time. Arthur describes Isaac as being a "good kid" and remembers him fondly.
One day when visiting the pair, Arthur found two graves in the ground outside of the home and immediately knew that Eliza and Isaac were dead. He learned that they were robbed and murdered for a meager amount of money (ten dollars). Arthur never fully coped with their deaths, and the incident had a profound impact on Arthur's loyalty to the Van der Linde gang, viewing them more as family and holding disdain for John Marston for leaving them (including his own wife and son) for a full year.
Events of Red Dead Redemption 2
During their fishing trip, Arthur tells Jack that he once taught another young boy to fish. Jack asks if he's refering to Lenny, to which Arthur responds that he isn't and that this was long before he met Lenny and that it was even before Jack was born. He is most likely referring to Isaac.
Arthur can mention Isaac when conversing with Rains Fall, voicing his concerns of Dutch van der Linde's interest in the tensions of the Wapiti Indian reservation and the US Army, particularly the involvement of Rains Fall's own son, Eagle Flies.
If "Of Men and Angels" is completed and Arthur has high honor, he will meet Sister Calderón at Emerald Station during "The Fine Art of Conversation", in which Arthur mentions Isaac when conversing with her.
- Red Dead Redemption 2
- "A Fisher of Men" (indirectly mentioned)
- "Archeology for Beginners" (mentioned, determinant)
- "The Fine Art of Conversation" (mentioned, determinant)