Yes, there are plenty of otherkin with multiple kintypes. I can't even tell you how many I've met online. It has to be dozens at this point. Though personally, I can't imagine what that's like. I only have the one.
As others have answered, it is possible to be more than one theriotype or just type in general. There tends to be various descriptors for this and they depend on just how or what they are. While a wolf-fox might not be an actual animal type itself, as no such organism regularly exists, it could well be something else, there is nothing inherently preventing that just as there is nothing preventing being both a wolf and a fox. If one subscribes to a common sentiment of reincarnation, that is an efficient way to imagine it, just it would be fair to use any number of multiverse theories wherein one could simultaneously be, or have been, both these things at the same time in two different places and existences.
As one can see, there is no shortage of explanations of possibilities, but what is important in that is deciphering what it means to you from each source.