Documents for purchasing property inherited by will

Hello Friends,

I am trying to buying a land in my native place in Tamilnadu. The land owner is a known person to me.  The land is agriculture land.

Let us assume He is S1 and his father is F and he has a brother S2.  F inherited properties from his ancestors.

The land i am going to buy and another property are given to S1 by F through a registered Will (not probated).

S1 has patta/Khata in his name for the land. S1 has a wife and 2 children (one major and one Minor).  

Now when I buy this land what are all the documents i need to look for. I am currently offered with

1. Copies of original combined land the F got from his ancestors

2. Copy of the Will made in favour for F1.

3. Copy of the will made in favour of S1 by F1.

4.  Application for Patta/Khatha transfered to my name post sale of the land

5. Witness sign by the wife of S1 and the major kid of S1 in the sale deed to me.

Now what are all the additional documentation required and an relinquishment letter from wife and kids of S1 required? or any interest of minor has to be cleared?.  What would be the role S2 (brother of S1 in this)?

Is S1 is sole owner of the inherited or he owns only 1/3 or 1/4 of what he own and is the children and wife of S1 also has share in the inherited property?

Thanks

Sathya