Ancestral property

After the death of a person it is compulsory to register legal heirs however if you have not done yet ,you can register it now in concerned registrar office,No A can not sale whole share ,being a ancessostral property the children of A will also have share in this property.But wife will not get anything.It mean if A has 2 children no matter son or daughter,the property will divide equally in 3 share .

1.  Grandfather purchased the land and made agreement thus this land was registered on your grandfather name or not

2. if it is registered on your grandfather and after his demise the said land was divided into two parts and divided to their sons i.e., is A and B and it was only agreement as per your query means now on official records if it is registered by your grandfather and if your grand mother is alive then the land will be divided legally into three parts and to be registered 

3. but now you do not want to sell the property being grand son 

4. even for registration you have to take court permission for legal succession and then register the property into three parts i.e., your father, two sons 

Another most important feature is Possession and enjoyment and such status shown in revenue records. As an individual however intelligent he may be, it is always advisable to contact a dependable and honest lawyer to guide you.  Through forums, litigations can not be solved.  At the most it may guide and ultimately your learned advocate may hear others or may not.  Before it is too late contact advocate.

From your query it appears that the grandfather who purchased the property himself has not got the sale deed executed and registered, the purchase remained at agreement level only though the possession was taken over and subsequently the property was divided into two parts by each of the two sons having possession of their own share  of the property and even this was not under a registered partition deed.  Under the circumstances, owing to the long possession of the property, if both the sons of the grandfather are alive, can draft a partition deed based on the grandfather's agreement of purchase and subsequent possession, register the partition deed before the registrar on their name and continue the enjoyment of the property. However, this being own property of the share holders on acquiring it through partition, the children of the share holders are not entitled to any share in the property and the share holders have all the right to dispose it in any manner they desire , neither an injunction nor a share can be sought legally.