Property Dispute

Greetings Team, I have some query regarding our property.My father had some property which he got from his mother by dividing along 3 Sons among 3 one of my Son is my father and 2 son sold to others but my father bought giving money to 3rd party its in my mother name and other 3 son sold his property to another . Apart from 3 sons our grand parents having 2 daughters who are married long back in the year 1982 and 1983 . Now one of the daughter had put case on my father he need property from my father .All this property divided long back almost 25 years.2 son was died long back 3 son sold property long back to others .remaining is our property only . And other main thing is our grand father had 3 wife . All property has been divided on basis of wife names.Our father is 3 wife son (above all 5 belongs to 3rd wife) . Please advise weather we need to give our property to my father sisters ? we retained our property with lots of struggle in early days we took education loan and borrowed money from others for our daily needs we struggled lot to retain since 25 years .Now this peoples put a case on us .. Please advise on this . Thanks in advance . we are waiting to hear from you .Please advise .