My father has different surname due to clerical mistake

Hi Sir, My Name is Ramesh Babu Bhimavarapu. I am writing this mail regarding a problem with my Father’s Surname My father name is “Ranganayakulu”. His Original surname that came from his parents is “Bhimavarapu”. At his 10th class, the school clerk entered his surname as “Velugoti” instead of “Bhimavarapu” by mistake. The same mistake carried over to his 10th Class Mark list and further education documents. He got State government job based on his education. So the same mistaken name carried over to his job related documents and records. Since my father doesn’t have sufficient knowledge about correction mechanisms, he couldn’t take any corrective steps.He is retired now. Now All his education and job related documents have INCORRECT surname(VELUGOTI). On the other side he got some other documents like ration card which got based on his name on his paren’t ration card which has Original Surname(BHIMAVARAPU). The other set of document which are derived based on his ration card like VoterID, Bank accounts, Land and house documents have his ORIGINAL Surname(BHIMAVARAPU). And all his kids(including me) carrying his ORIGINAL Surname(BHIMAVARAPU) as per the ration Card. The crux of the story is, he has legal documents which has 2 different Surnames. His Kids and His parents has only one surname. Now How can we correct and clean this mess without creating more problems now and in future? What are the best solutions and options does we have?