so what happens to isaac in the genderswapped au, seeing that arthur (martha) raises him (her?) in the gang? love ur art !!!
Thank you!! Alright, so I'm just spitballing here, but in a genderswappwd au, I think it is more likely that Isa (Isaac) stays with Martha (Arthur) since a child's mother being in the gang, to me at least, makes it very very unlikely for them to grow up outside of it.
Since it's the first time this has happened in the gang, everyone needs a while to get used to this. I'm imagining that Martha is in her early twenties, so Jane(John) is about 13-ish and had just been picked up by the gang only a year or so ago. Jane is curious about the kid but incredibly scared for Martha during the birth (idk if I'm remembering this correctly tbh but I THINK this is mentioned once) since her own mother died during childbirth. That might actually also be a motivation for Jane to run away when she gets pregnant and have Jackie away from the gang, terrified of meeting the same fate as her mother. After Isa is born though, Jane undoubtedly sees the little baby as her younger sibling/niece and the same goes for male Tilly (haven't figured out a name yet). Though I think Jane is less likely of the two to be allowed to babysit the kid on her own.
Butch (Dutch), Hosanna (Hosea) and Saul (Susan) help Martha out the most, sorta like when someone has a kid very young, its often the grandparents helping. However, I think Martha is still quite present though she battles with the guilt that comes with bringing a child into a broken and dangerous environment. In the canon story, for Arthur it seems to be more about responsibility and inability to truly be there for his child. I can also imagine that there's a certain vulnerability that comes with creating something precious like that when you're used to a hard outlaw life, and I actually believe it may push Martha towards a slightly different course of actions, knowing there is someone to cherish and raise (though I am not a fan of using motherhood as necessary for female redemption!).
I haven't decided if I'd rather mirror cannon and have Isa die or not. On one hand, being surrounded by a such volatile environment, she is at more of a risk, but there are also more people willing and able to protect her. If I wanna be nice and say she does live, during the events of rdr2, she is in her early teens, similar age to Jane when she joined the gang. Martha may feel conflicted on letting her participate in any of the outlawery OR she may actually feel a responsibility to really teach her how to survive in a harsh world like theirs.
Once Martha dies of TB, Isa most likely goes with the Marstons. It'd be nice to imagine her like an older sister to little Jackie(Jack), but by then, I find it also plausible for her to have grown into an outlaw despite Martha's warning when her life neared its end. Perhaps, Isa is also wanted by the law. Perhaps, she is just another person for Jackie to lose.