- Since your grandfather got the said property from his father , hence after receiving the same it become his self acquired property , and he was having his right to transfer the same as per his wish , and none having right to claim.
- Further , if the settlement deed is registered then it cannot be cancelled now , but if the said deed is not registered then this property would be devolved upon all five sons equally .
- Your father should issue a legal notice and ask his 1/5th share in the property , even now it is constructed by any brother .
- If, no response , then file a Partition and Permanent Injunction suit before the court for getting his share and to restrained them to transfer the said property to third party.