Who can be considered as legal hiers

My father bought 2.5 acres of land in 1998, it is actually a 300 acres of land which was divided in between several brothers, but the dividation is not done on paper but orally, the land that we bought, is road touch and so we also payed high for it, the land is registered in my mothers name, with it's demarcations mentioned in the document, the document also contains signs of the person who sold it(the grandfather) his sons, daughters. Now i want to sell the land but some people are spreading rumours that the dividation was not done on paper so the land does not actually belong to us, these some people are the brothers of that grandfather who sold it. My question is, do they have any legal right over my land. Is it possible that i can be asked to choose another land in that 300 acres which is not road touch. Can i sell the land without needing any permision or clearance from these people. Can they file any case against me or the buyer in case i sell it. And what if such a case is filed before or after i sell the land, what are the chances that i will win that case in my favour. Thanks in advance.