Urgent - ancentral property claim rights for grand children

Hello Everyone,

 I am in the process of finalizing a property in Bangalore which is a Joint development project between the land owners and builder. I have an urgent query and need your help. Here are the details - 

1)     Settlement deed entered into between A & his wife B and their children C, D, E and F

2)      Few years later WILL executed by B (mother of E) in favor of E

3)     Later JDA entered into between E & others (his 4 sons G, H, I and K) and the Builder.

4)     GPA executed by E & others (his 4 sons his 4 sons G, H, I and K) and the Builder

5)     Khata extract issued by BBMP in the name of E

6)     Family settlement deed executed by E along with his 3 sons G, H, I in the favour of his 4^th son K

7)     Final sharing agreement entered into between J and the builder

Now K is the owner of land for all legal purpose as per the family deed settlement in which his father E and his brothers G, H and I have signed but none of the children (major or minor) have signed on any of these agreements.

My question is –

1)     Will this land be called as ancestral property? If yes for whom?

2)     Can someone explain the four generation rule for considering a property as Ancestral with the names mentioned above? For better understanding.

3)     Can children of G, H, I and K file a case to claim their share in this property by any means today or tomorrow?

4)     If yes what precaution I must take to avoid such issue in future to safeguard my buying interest?

 Note: Builder is not ready to add any additional clause in the sale agreement/deed and he is adamant on that.

 Please suggest on urgent basis.

Thanks a million in advance.