Nominee has to pay tax for Interest earned from Parents Account?

Since my parents passed away, I had to close all their Post Office Kissan vikas Patra Accounts as I was the Nominee on all their accounts. 

Now the interest earned from their accounts credited into my Income tax AIS statements, But the whole money distributed to all My Sisters and did not take single Rupee from the whole withdrawal. 

I have Post office Interest certificates Statements and also the accounts mentioned there belongs to my parents accounts and I have the relevant account numbers passbook with me.

Can you please suggest on this situation and how to avoid tax on me.

Thanks

Palani