What is the penalty(s) for commiting what I consider fraud on a Power of Attorney?

We learned that my mother signed a Power of Attorney to a brother and later learned that a sister's name whom my mother didn't authorize is on the POA. The POA was also signed by my mother at a house that she lives and that I own and notorized eventhough it wasn't signed in front of the Notary. The POA was recorded on August of 2012. My brother on the POA is fighting for the house that I own and is causing a lot of problems, even to the point of lying on the POA. Also, my mother is 86 years old and is of sound mind since she was recently evaluated by doctors. She is hard of hearing and has very poor vision and uses a walker to get around. Can my brother be held liable for what he did, that is, lying on a POA?