Hi, Took in two kittens (sisters, same litter, about 12 weeks old) about two weeks ago. We are kind of new to cats so I'm not exactly sure, but should they both be purring? One is and the other isn't (or at least is not in front of us). I read that purring in cats is actually the result of the vibration of a major blood vessel. Do all cats purr? Does it necessarily represent a health problem if they don't. Sorry if this is a bit of a dull question, but with a new animal I figure its better to ask and look dull then be wrong and look duller! Thanks in advance.