Division of grandfather's agricultural land among legal heirs

My grandfather has 8 children. In which 6 are sons. He divided his agricultural land in the name of his children in the year 1970 through a partision deed which is registered. But in the year 1980 my father and his younger brother exchanged the land given in partision deed between them through the formalities in Taluq office(through 21form) by mutual understanding. From past 36 years we are using the land which we exchanged. We have plantation done. We are paying land tax to the lands we exchanged from past 36years. And even we have taken loans from bank. But these lands are transfered to me nd my brothers from my father in the year 1993 through panchayat palparikat(not registered)which includes the sign of my fathers brother too from whom he exchanged .My fathers brother and his wife passed away 13 years back. But now their four daughters are claiming for the land given to their father in 1970. How will this cause problem to us?Plz suggest.