Hi,
Don`t be hasty, you don`t know who this cat belongs to, if anybody. So in the mean time you can feed him, but if you start this be prepared to become his adopted family in the future. Your dog and cat will be wary of him, as this is natural territorial behaviour. I myself have been adopted by a homeless cat, but i know she is homeless because distant neighbours just moved and left her.

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Amanjay Siamese & Animal Healer.