Self acquired property

Hi, I need your best advice for the below case. Case details: My dad owns a property of 5.8 acres, which was bought through a sale deed in 1980's. The property which my father bought was sold by my grandmother to a 3rd party. My grand mother had 5 children, of which only 3 have signed it. The legal heirs of my 4 uncles have come to claim the rights on the property. 1) We have got the consent agreement signed by my grand mother and uncles. Therefore, does my cousins have any legal rights on the self acquired property of my dad. 2) My cousins were not born at the time of the sale deed through which my father had bought the property. 3) The consent agreement signed by my uncles claim that they or their heirs or there heirs would not have any rights on the property and any legal actions against that property should be dismissed outright. 4)Can i file a criminal suit against my cousins who are attempting to grab the land by misusing the law of this land. Ur assistance is appreciated