How to divide the property?

Hello, I am the youngest son and I have two elder brothers along with my mother. My father expired suddenly when I was 5 years old. So my mother had to go through lot of stress and had to face many family problems. Besides these problems she raised us properly. My father has two younger brother and they are very selfish and fighting over our property since 26 years till date. Due to my fathers sudden death my had no idea of any kind of documents and life certificates, pensionary benefits documents etc. So my fathers younger brother convinced my mother and took all of the documents by saying that he will help get all those benefits what my father had to get, so my mother trusted him and agreed to his words. Now that he has all the papers and documents he is not willing to return them back. When my father was alive, there was meeting with our society and our property was divided into three parts and there were few witness at that right time along with a piece of paper and signatures of my fathers brothers. We had two lands in two different places and my father and his brothers had equal right on it. So my grandmother decided to divide it among them in the presence of few elderly persons of our family and it was written on a piece of paper along with signatures. Now, one of my fathers brother sold his property and as he had no place to stay we called him to our house and asked him to stay in our house. As time passed by he was good to us and we trusted him more than the other brother of my father. We had leave the place for some reason, so my mother singned him as the power of attorney so that he could look after our property in our absence. Now, he is asking share in our property as he sold his own but didn't give us any share even after we had shares. So he filed a partition case. What should I do now and how do I take the power of attorney back from him? Please help me find my answers.