My fiance has likely had his signature forged on a power of attorney document. What recourse do we have?

My fiance suffered a bad stroke August of 2007. He gave me his power of attorney, and I took care of him and everything that  needed to be done. He has a brother who lives in Florida and a son who lives here. At the time, his son was not having anything to do with his father, and the brother was more than happy to have me take care of everything. In January of 2008, I became ill and could not go to the nursing home for about three weeks. I was put on medication that I had to become used to and could not drive for a while. His brother has come and convinced my fiance that he has taken care of all his business, which is way far from the truth. He revoked my power of attorney. When I saw the signature, it was obvious that it was not my fiance's. When I talked to him he said that he did not want the POA changed and that his brother had taken his hand and signed his name for him. The emotional and mental stress from all the things that have gone on since I got sick is horrible. Now the son and his wife are back in his life and they all are trying to keep me from my fiance. When I do go to see him, he tells me that I am the only thing that keeps him going. What should I do? I have been told that the power of attorney is not legal if it is not actually his signature. What recourse do I have for that and do I have a case against the stress that I have gone through? Thank you.