Property purchased from joint fund of monies received in compensation of property lost in pakistan in 1947?

two brothers came to india from pakistan due to partition in 1947.they jointly applied for claims of self acquired properties of their father lost in pakistan.meanwhile one of the brother died.his share of claim fund was made in the name of his widow and 2 minor sons.the widow purchased a property from the said claim fund in an open auction.got leasehold rights which later she got converted into freehold registered rights after payment of dues.now after 30 years one her sons is claiming share in her property being an ancestral property and joint property, and the payment being made from joint fund.moreover he is playing on fact that the fund was of 12000 Rs. and property was purchased for 8000Rs.,way beyond the amount of widows own share in the said fund .what can the widow do to defend her clear title in the said property?