1. Why did you not got the sale Deed Registered in your name, by paying applicable Stamp Duty?
2. Are you aware that you cannot get proper legal title/ownership of the property on the basis of GPA, Agreement to Sell and WILL?
3. Now, whether the person who gave you the GPA is alive or not?
4. Whether the Agreement to Sell is registered or not?
5. Whether the Agreement to Sell indicates the amount of consideration paid by you, and possession of the property given by the seller to you?
6. The property is situated in which City/Town/State?
Without knowing the details to each of the above query, it will not be possible to give answer/solution to your query.