Jack Marston - 1914

Born into a gang of criminals, Jack's upbringing was that the gang was family to him and he called most of them his aunts and uncles. A comment from Jack himself in 1907 suggests the gang not only cared about him a lot and tried to keep him out of their illegal activities, but also avoided mentioning them to the boy, yet Jack still managed to deduce something about it by himself. One of Jack's most dominant traits was his fast learning: at 4 years old, Jack already possessed basic literacy skills, and he learned the basics of fishing from Arthur Morgan. Despite being fairly open and comfortable around people at the age of four, he was considerably more shy and reserved by the time he was twelve, and began to feel inferior to his father. As a result of his upbringing, Jack initially lacked his father's courage and superior combat, farming, and survival skills, but possessed intelligence and empathy that far surpassed John's.

Marston ranch, all happening in a very short amount of time, greatly darkened Jack's personality. His grief and loneliness appear to have developed a severe case of depression and self-loathing. He also developed an intense hatred for the American government and its law enforcement organizations, deeming them the real criminals and the people responsible for the demise of his family.

Jack's deep love for his family also ironically results in becoming the very thing his parents did not want him to be: an outlaw. It was this love and grief that led him to hunt down Edgar Ross three years after his father's death, determined to avenge the Marstons even at the cost of his own innocence and potentially his future. In his quest for revenge, Jack kept a rather calm and friendly demeanor, and had his anger in check, only showing his intense hatred for Ross when the latter dismissed John's death as his own fault upon being confronted.

Jack's general attitude, character and personality in 1914 is very reflective of the player's honor level. If Jack has a low Honor level, he will in turn have a sadistic, belligerent attitude during gameplay and often makes dark jokes whenever he kills a horse, an outlaw or a woman, but also shows signs of disgust at himself and questions his own actions. When approached by a prostitute they will be disgusted with Jack and turn him down.

If Jack is played with a high honor level, his attitude is far more depressive than sadistic. While helping strangers Jack will often lament that he has nothing to live for. Jack's dialogue with pedestrians will be more friendly but also jaded and somewhat somber. If approached by a prostitute Jack will instead turn them down and may remark that his family would disapprove, showing that he still values the morals his family taught him.