Owner sold property twice

My grandfather bought a property on August 1954, in that sale deed 3 items are independent 4th item combinely with two other close relatives, 4th Item is 41 cents of land. Each one will get 13.66 according to the sale deed on 1954. In 1984 one of the party in the sale deed sold combine property 41 cents, to other party with out informing other 2 parties.We got to know when he is trying to sell 3 items, and did surveying of the land beside to us. There we got to know that he sold the property of 41 cents to with out our concern, and we asked him, his reply is you were in not in possession and enjoyment of the 41 cents, hence he sold that property. We are actually in enjoyment, we have the proof of bank loan had taken and cleared. Also government has given subsidy for the loan since the loan is agriculture loan. After clearing the loan in bank in 2016, In 2016 we have given that land combine with 3 other items we bought in 1954. Since the land has not have any construction, my question is that how to make the other party not enter in that land, and also how to prove that our land is in enjoyment and in possession. How to avoid adverse possession suit by any other party. Please suggest thanks in advance.