Guilt, family and redemption are core themes of both their story arcs, and the way their journey and issues mirror and complement each other.

If for Sebastian it’s a desperate fight to cling on to what he has left, to preserve that family because up until then he’s been going through it all alone, with no support or help to pull him up from the depths he’s sinking to. But Arthur’s generally friendly and surprisingly supportive, appeal to empathy and he’ll help; if Sebastian needs a friend, Arthur can be a friend. On the other hand, Arthur had a lot of people there but not many of them open to his struggles (he himself isn’t allowing close people to pry into the way he’s feeling), but damn if he won’t open up to strangers, tell them he’s feeling like shit right after saying hello, because for Arthur’s looking for a break with the people that are stifling and enabling him to do his worst. And if Sebastian’s just a stranger, there for a chat, for a moment of pouring out mutually vulnerable experiences that’s exactly what Arthur needs.

And that’s not even mentioning parenthood and how important it is to both of them, Sebastian’s definitely a family man, without it he just sunk into work and alcoholism, but for Arthur too: he regrets losing Isaac so goddamn much, and the way he treats and interacts with Jack, the way he begs and fights tooth and nail till the bitter end so that John doesn’t lose what he has lost. If Arthur met Lily he’d let no harm come to that girl – by extension Sebastian. Arthur has another chance at being a father; Arthur has a chance at a different life, one to appease his own mind and dreams, to make of it what he wants not just what he got the chance to because he was the lowest rung on the social ladder as an orphaned child of an outlaw. And it’s a chance at a different life for Sebastian, not alone, with a friend, someone dedicated to taking care of his daughter with him, someone he can unwind and roam with.

And that’s how their paths to redemption collide: what else better than the prospect of family to spur Arthur away from Dutch, to put a stop to outlawry and do right by people again, what else better than just one someone that sticks with you to help Sebastian pull himself together to finally heal and sort his own shit out, not because they’re incapable of doing that on their own, but because it makes it easier, more pleasant.

And they just have a similar sense of humor and tendency for rough coping mechanisms like drinking, smoking or violence/reckless behavior – leads to injury, disease. Maybe that’s why I tend to write them meeting half drunk, spilling their vulnerabilities out, until they mount into a tension that can only be resolved in a fist fight or sex. It’s not healthy, but it’s what they got, for now... For now... And, now that the deed is done, they’re involved, so they have to do better; they met at their worst already.

From here on feelings become more nondescriptive and much more suited to being written in a fanfiction plot i think.