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Firstly, I have the strong belief that Molly (by the start of the game) only very recently started dating Dutch, and on top of that, was part of the gang for a while before dating him. I'm so certain of this because of what Karen says in chapter 1 during the mission where Arthur takes the girls to town where she says "Oh no, miss O'Shea is far to high and mighty now for the likes of us" when Tilly asks if they should've invited her out. What's stands out is the now, becuase it wasn't a 'hey now, she's too good for us' it was a 'she is too good for us now compared to the past'.
This shows there was a point in time where she was in the gang, but wasn't dating Dutch. But once she did get with Dutch she felt she was too good for the girls, which you can see through the fact she isn't hassled by Grimshaw to work, sleeps in a tent, and has really fine clothing compared to the girls.
This had me thinking about, when did she join the gang? I thought, maybe she was part of the six month gang with Micah and Charles, and I thought that introduced a really interesting dynamic. Because, I personally, when playing the game for the first time, assumed Micah had been in the gang for years because he appeared so used to being with the gang, and the gang obviously didn't like him, but seem used to him too, at least more used to him then they were of Charles.
And in the hunting mission in chapter 1, Arthur assumes Charles would be "moving on" soon, and asks him about it. But, as much as Arthur talks about cutting Micah loose, he doesn't assume Micah will. And I noticed the common denominator of the six month gang, whether or not they're seen as a part of the gang and an outsider, is Dutchs interest in them.
Obviously, he's romanticly involved with Molly, and freinds with Micah, but doesn't have any connection to Charles. So, obviously Charles' quietness contributes to how lonely he is, but Dutchs approval of people also contributes to how the gang (does or doesn't) approache(s) them.
So, Dutch was interested in Molly, so she was freinds with the girls (even though once they got together she felt above them), Micah has Dutchs approval, so people tolerate him. But Dutch doesn't think about Charles, so no one thinks about him. And it shows Dutchs iron fist over the gang.
Another idea is how each chapter Arthur and Charles become closer each time, possibly representing how each chapter Arthur strays further and further from Dutchs authority.
Also, the fact people who befriend Charles seem to stray from Dutch...I dunno I just remember a camp interaction where Uncle criticises Dutch, and similarly there's another camp interaction where he is truly trying to befreind Charles, but he's not having it lol, so it sort of creates an idea of how he's hesitant to leave the gang therefore it's represented with a struggle to be freinds with Charles.