Patta, Pathiram clarification

I am from Pollachi, Coimbatore dist. In 1994 Mr.Kupusamy received 'Manaivari thoraya patta' from the Tamilnadu govt for 2.93 cents. Moreover, In 1998 he sold 2.93 cents to my father. In the sale deed document, Kupusamy and my father signed. Now Mr.Kupusamy's 2 sons saying that without their sign how do you buy this property. Sir, can you please clarify for me whether it is necessary to get the sign from Kupusamy's family members. Ask your legal doubt about Patta, Pathiram clarification | Get the best advice and Consultation. Top Lawyers in Chennai, best Law firms in IndiaPopular Questions:https://www.lawyerchennai.com/legal-consultation/legal-consultation-for-a-firm-and-firms-property-case/https://www.lawyerchennai.com/legal-consultation/legal-support-for-company-debts-bankruptcy-and-partnership-disputes/https://www.lawyerchennai.com/legal-consultation/can-i-get-free-legal-service-with-a-winning-case/