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It sounds like these two are both showing neurologic signs. In young, unvaccinated kittens, I would be concerned about several different things: rabies, toxoplasmosis, feline infectious peritonitis, cerebellar disease (a congenital defect), etc
These kittens should really be examined by a vet. I would start with a physical and full neurologic exam to try to locate the neurologic lesion (brain, brainstem, nerve-muscle junction).
These kittens may have a poor prognosis.
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