Wher & how I can get the original deal paper b/w builder and Owne

My Father has given a Power Of Patterny of a land To My Cousion Brother. Actually we have a land together around 12 Katha(50% is My Land And 50% My Bare Papa Land). My Cousion( my Bare Papa's Sons) took a responsibility to deal with builders to build appartment and we have some shares on them. My Father always signed on paper whenever my cousign brother told to him. Now after 5 year Apartment with 4 floor and 16 flats(3Bhk) is ready. My cousign brother now share 1 flat and less then 1lakh to my father to my father. Even they didn't give choice flat. Now every one is telling that my cousign brother has done some fraud. As there is 2 or 3 flats in his share. he told to my father that remaining One/two flats from his share is for broker who was involved on this process. The ownership paper of flat given by him to my father is ok. Every thing is ok as per papare. But I have a dought that he has done some froud. I feel that Builder and My Cousign brother both are involved in froud. As My brother's relation is very good with builder and my father know the builder but not too much. My Query is 1. From Where and how I can get the original deal paper between builder and My Cousign Brother? 2. From Where and How I can get all the details of paper which give me all the details. 3. What Paper will give me all the details.