Dating gang members
The loss of his son and Eliza made Arthur appreciate the family he had in the Van der Linde gang and perhaps fuelled the frustration he had with John when he ran away after getting Abigail pregnant with Jack.Arthur and Dutch have a long history together, with Arthur seeing him as a mentor and a father figure who taught him the life of an outlaw and embraced Dutch's view of a life free from modern civilisation and its rules.She asks if its too late for them to have a future together and asks if they could run away together.Arthur admits that he reciprocates her feelings but declines, stating that they need money, that there's still people in the gang he needs to protect, and that he doesn't want her to get hurt. Mary sends Arthur another letter with the ring he gave her a long time ago.He later learned that they were robbed and killed for a meager amount of money.The incident hardened Arthur ever since and he never truly coped with the pain.Not much is known about Arthur's relationship with his father, though the little information given implies a strained one at best.
Arthur mentions Isaac when conversing with Rains Fall, telling him that the incident made him realize that he can't expect good things to happen to him with the life he led.
In said letter she says it is time to cut ties for good, knowing that Arthur will never change, while also apologizing for the pain their failed relationship caused him.
In the epilogue she is seen visiting Arthur's grave, mourning him, and the ring is used by John Marston in his proposal to Abigail Roberts.
Arthur mentions Eliza when conversing with Rains Fall, admitting that the incident caused him to believe he has no right to expect good things to happen to him because of the life he has led.
Eliza and Isaac's deaths have also deeply affected his loyalty to his gang, considering them as his family, and holding disdain for John Marston for leaving Abigail Roberts when he got her pregnant with their son, Jack.Eliza knew of Arthur's criminal background but had accepted any support Arthur offered to her and Isaac.