Land dispute

A family along with 3 other neighbour families staying in their respective houses they received from their fore fathers from last 60 years. But recently they received a notice from other neighbour hood who started construction in his piece of land surrounded by the families that the land where the four families are living from past 65 years belong to him and also stating that he had a document registered in the year 1948 which was purchased by his grand father. Does any one provide me a solution for this kind of situation so that I can guide them the right approach for justice.