Dear Mr. Kapil Sharma (Advocate)
You don't seem to have understood the problem in its entirety.
A will (whether registered or not) will come into operation only after the death of the testator. In this case the Testator is alive. A Will will become inoperative when the person in whose name the will is given predeceases the testator. Further, a Will can be revoked by the Testator at any time.
So, when the title of the mother itself is in question, the inheritance by her heirs is inconceivable.
Mr. Deeksh*tulu, I wonder who will file the suit for specific performance. The person who bought the property some 13 years ago under power of attorney is not available any more. She ought to have asked for execution of the Sale Deed. Having not done so, is there not any limitation for seeking 'Specific Performance'?
Mr. Tyagi (you seems to be a Telecom employee) at best you can rely upon 13 years possession to claim title due to 'adverse possession'. Do not approach the seller at this time. Keep quiet for some time. After 2-3 years file a suit for declaration of title (in your names). It may take time, but the other party would not be in a position to do anything to you. Similarly, till such time you have clear title to the property in your names, you would not be able to dispose off the same. But there will not be any difficulty in continuing to live in the property.