The kitsune racial feat Myriad forms allows you to:
With a bit of self-discovery, you find a new form. You gain the alternate form of a kitsune heritage other than your own, adding it to the options for your Change Shape.
The heritages give you either a fox form or a tailless form, so I imagine this feat was designed for those who wanted both a fox and a human form. However, the wording is the same on the tailless form heritages:
Your alternate form is a common Medium humanoid ancestry prevalent where you grew up (typically human), called a tailless form.
Does this mean you could take the tailless form a second time, say your heritage is frozen winds and the heritage other than your own you choose is celestial envoy to get two different appearance tailless forms? If so, would they need to be the same ancestry? Assuming that you didn't get to pick a new area you moved into and you were still restricted to the choice from those "prevalent where you grew up", Webster's has two different meanings for prevalent that I could see using:
1: Widespread, as in Red foxes are very prevalent in North America, Europe and Asia
2 Dominant, as in: The prevalent species is the free-tailed bat
If you grew up in a cosmopolitan place with two or more ancestries mixing, I can easily see being allowed to pick two different ones in the "widespread" use (Assuming we get to pick two tailless forms to begin with, and not just one tailless/one fox), but if it means "dominant" then that implies there's only one dominant ancestry. That reading seems less likely to me, because it would preclude anyone who grew an area without one ancestry having a majority (Or at least large plurality) from being allowed to pick any tailless form.
Is there a clear RAW here, or would it be firmly in the hands of the DM to RAI it?