[@Pathfinder] Oh yeah, I almost entirely forgot about that. My idea (and I'm willing to hear others) is that Rat Beastmen and Rakeesh were that they used to be the same race, but a group of Rakeesh intentionally broke off from the main group to go and live in the kingdom, as citizens. Eventually, they mixed enough with humans to have a more humanoid appearance, less hunched over and no bent legs. If you have another idea though, I'd be willing to hear it.