Right against ancestral land

Dear Sir/Madam I am vipin kumar from delhi, I would like to ask you about my ancestral agricultural land. That in the year 1954-55 my great grandfather named (Bhika) got the bhumidhar right on a certain piece of land in Delhi for which we have got the official records with us. According to which, the actual bhumidhar of that land was my great grandfather Bhika, whereas his brother got his piece of land somewhere else and got the bhumadhari right on a separate land. Therefore, after the death of my great grandfather, the ownership of the land should only be transferred on the name of my grandfather who were the only child of my great grandfather(Bhika). But dont know, how the children (successor) of (my great grandfather) bhika's brother got involved in our land which was purely on the name of our great grandfather. the khatauni described it as like (adesh anusaar) the name of the children of my great grandfather's brother got introduced in it. Previously they used to say and confirmed to us that they would by their witness make it tranferred on our name but due to the high prices of land now they have turned back and claiming their right over it. Sir my question is when we have got the pure bhumidhar right upon our great grandfathers name then how come the children of his brother could claim their right over it and also they officially had maintained their names in the khataunis later on, where my great grandfather did not do any sale deed or any kind of negotiations with them. Sir please help me out in this so that we take this issue on further stages.