I think that Tantomile and Coricopat are, in fact, the spirit of one cat (Tantomile, I think, as females, in general, have greater mental abilities than males) in two bodies. That is one possibility.
The other is that POSSIBLY Tantomile is the only real cat we see, but that she has conjured up Coricopat as a mate/friend.

Disclaimer: These are my opinions. I don't mean to offend anyone by them, and you shouldn't be offended by them, because they might not directly reflect the character from the movie.

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