I will suggest that you really just need to work it out, unless the cat is some rare exotic breed worth a ton of money, it will be a situation you need to work through because I doubt you will want the hassle, time, or cost to litigate this. The costs you are aging are offset a lot of times by the companionship of the cat and the enjoyment of the animal... Work it out because it jst seems that the law won't be your best way to resolve this.
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It appears that your brother abandoned the cat 3 years ago (age 15). I would suggest that you license it and treat it as your own property.
I am an Attorney-at-Law, licensed to practice law only in the state of California. Unless we have both signed a formal retainer agreement, you are not my client, and my discussion of issues does not constitute legal advice. Opinions expressed herein are those of the author, and do not necessarily represent the opinions of those who hold other opinions.
There is no clear answer to your question. It would be left to a court to decide if you went down that road. If he tries to bring a claim against you asking for return of the cat, you could counter claim for all of your expenses for the care of the cat. Potentially, there is also an abandonment issue, but that is a state specific definition and I do not practice in CA. I would consult a local attorney if you truly want to keep the cat.
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