1. If your father is one of the shareholders of the property then the sellers are required to take your father's signature in the ale deed or should take POA from your father,

2. In the said sale deed or POA payment of his share should have been mentioned,

3. How and in what capacity your father's elder brother has collected the share of your father?

4. If he was authorised to collect money for your father and now refusing to pay him, lodge a police complaint against the said person,

5. Your father can file a Recovery Suit against his elder brother claimh his share with damage and interest on it.

1. If the signature of your grandfather was not taken by the sellers or if your grandfather has not executed any POA in favour of the sellers for selling his share of the property, then he can file a partition suit claiming his share of the property,

2. Engage a local lawyer having experience in this field for the purpose.

1. Your father can file a lawsuit for partition to cull out his share in the property and also seek a stay order against the sale till such time that his share has been separated.

2. The registrar cannot either stop the other co-owners from selling their share or refuse to register the sale deed. He is bound to register the sale deed upon presentation for the same.

3. A criminal case for cheating can also be filed against the other co-owners if they sell the entire plot and pocket the sale proceeds without disbursing your father's share to him.

If this is an ancestral property, even you have a share out of your father's share, hence you may also approach court seeking partition, separate possession and injunction restraining others from alienating the properties till the disposal of suit. The registrar also may be impleaded as a party to the suit but for that a legal notice under section 80 CPC should have been issued or an application to waive the legal notice under the referred section is to be filed along with the plaint. You can include your father as a defendant along with others.