Hi
In response to your post, assuming that there is clear title flow from your ancestors to you, the same is answered as follows:
Firstly, the terms and conditions of the Agreement is a must to give clarity to your post.
What is the total sale consideration ? It will also have bearing on your issue.
Share the contents of two legal notices got issued by you. What for you got issued the said two notices ? The contents of the same will give us clarity based on which you can be guided accordingly.
Laws of the land and fundamental rights permit the citizens of India to raise issues pertaining to their respective fundamental rights before appropriate Courts of Law.
Going by your own post i.e., the other party is dilly-dallying and delaying the contract, if you go to court of law for adjudicating your issue, it can be concluded that substantial time will be consumed for first level of litigation itself.
The case on hand is pertaining to Property it can go to various Courts before logical conclusion is reached.
I am not trying to scare you, I am just bringing the real facts which you may face and I am being practical and realistic.
Further clarity can be given if you share the details as desired.
Good Luck !