Sale of Property by Heirship

I had bought a property in Kerala in 2007 from Seller A and got the mutation done and held since then. Seller A had mutation done on his name before the sale and had the land tax in place for my registration to be successful. Seller A had purchased this property from a lady (Seller B), her 2 son and her 1 daughter (All 3 Majors then) few months prior to my sale registration in 2007. This was after the single owner of this property Seller B's husband (56 yrs old man then) died and Seller B and her 3 children being the legal heirs. But I don't have the land tax in the name of Seller B and her 3 children, but the sale of land from Seller B to Seller A was successfully done and I have that original title for that too. Am being asked for Legal Heirship certificate or Family membership certificate of Seller B and her 3 children, when applied for a home loan. My question is 1. Could that transaction of Seller B to Seller A would have been successful without such proof of docs in the register office? 2. Could Seller A and now myself could have done mutation in Village office without establishing the required documents 3. Is there any legal risk that I need to be afraid of after 10 yrs of purchase and mutation of the property in my name.