I assume you are in California. Under this assumption, the power of attorney expired upon your mother's death. Your brother had no power to do anything pursuant to the power after that time. You need to speak with an attorney who handles probate matters, and provide him or her with all the documents you have, so that you can get some advice as to whether it makes sense to proceed against your brother or other person. The fact that your mother passed away 10 years ago may make this very expensive and difficult to pursue (and indeed, may make it impossible due to the statute of limitations), but it is impossible to tell that without a complete review of your situation.
Answered on Jul 30th, 2013 at 11:50 PM