I'm not sure it makes too much difference what sex the new cat would be as I reckon the cat's personality is more important. Our 3yo girls get on really well with Musky (10yo neutered male) but not quite so well with the two boys (19 months), nor with Musky's sister Twigs when she was still with us.

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Meet the gang - Musky Flori Phili Zeb Algy, members of the Catmint Appreciation Society