Nah, we can make this work. I'm not sure what you guys have already in the way of backstory regarding what's happened between Ossanlin, Myitt, Keslin and Keshin over the last nine months, but we can totally run with this.
My preference would be to leave whatever's happened somewhat ambiguous-- maybe something Ossanlin and Keshin don't like to talk about. Whatever this thing is, it was enough to secure Ossanlin's trust, and probably impress Myitt and Keslin as well. Give us a few months of demonstrated loyalty since that's happened, and we have a potentially-passable explanation.
Leaving it ambiguous has the advantages of, first and foremost, being kind of hilarious, and secondly, letting us figure out the details organically through the RP, at our own pace later on. If you guys already have details, more power to you ^_^ I look forward to catching hints about them.
Kells, Mar, don't change Keshin up too much for this. There's no reason they need to have become a trustworthy, upstanding first officer, or that they need to trust anyone around them. They're at their peak when they're a troublemaking source of chaos, and I wouldn't want to lose that. I mean, yes, for this to work, they do need to have some reason for loyalty to either Ossanlin or this group, and Ossanlin needs to have some reason to trust them... but, again, those reasons can be left more-or-less ambiguous. I almost feel as though Keshin would have to think there's some reason... some survivalist or opportunistic reason... to continue this 'loyality' thing. If that morphs into actual loyalty as time goes on (or doesn't, whatever), so be it, but for now, there's no real reason to be twisting these characters any more than is necessary. They are who they are.
I'll have a post up ASAP. Probably not tonight, but ASAP. My revised character sheets may end up taking a few days, though >.<