Uncle claiming share in the property what can i do.

Family Background: My Grandfather had 4 sons and 7 daughters. As of now 3 sons and 3 daughters are alive & all daughters are married before 25 years and given the good amount for grandchildren as well. One of the Son (bade papa) dead in 2004 due illness before to that his son and wife are also passed away but had three daughters(all are married). Property: We have a house in 600 square yards with two stair building on the name of Grandfather which is occupied by all 4 sons. Question: My father younger brother (next to my dad) is saying that whole property belongs to him. Because in 1994 grandpa wrote a will that this property belongs to grandma and grandma wrote a will to him in 2000 but all are bull shit and not valid. They have some signature of grandma and grandpa on white papers. Reason:My father (is 2nd son) & elder are signed on papers in 1979 to grandfather that they are divided from him for incometax reasons but didn't mention that this property belongs to younger bro.