7/12 name change

I had bought property in November 2010. I have Sale deed, Index II & registration fees paid receipt.

I didn't changed the name on 7/12 from seller to mine. Now I want to sale the said property but the seller has died & I don't have any contact with his family or where he is located. What will I have to do to add my name in 7/12 & also on property tax receipt