Property distribution among family

Hello, Thanks for providing a platform to seek legal advice regarding all sort of matters. Let me brief about my family and the case: My grandfather is expired way back in 1948. My grandfather had five sons and three daughters. The eldest son purchased a land and constructed a house in 1974 on joint names. Sale deed was executed in favor of eldest son and youngest son. Eldest son only put entire money to purchase that property, though as I explained earlier, He purchased the property jointly in favor of him and his youngest brother. Youngest brother is my father and alive, while the eldest brother who had put the entire money to purchase the property is dead in 2012. In 2012, the eldest brother, the first owner of this joint property has expired. He didn't prepare or leave any will. He had four sisters and no sons. All sisters are married. Now, other three brothers are claiming that they need equal portion of property citing examples of Hindu Undivided family. Though, we are not registered as Hindu Undivided family. Since, now property is in the name of youngest son( I. e. my father), will the other 3 brother hold any legal entitlement in the property. Will the four daughters of eldest brother(who was the first holder of the property and who already died in 2012) hold the legal entitlement. How much is the share for four sisters and my father. and other 3 brothers who are claiming that they need equal share in the property, will get any thing. They have put the case and summoned my father to give them equal share of property. What kind of documents, should we prepare to justify our entitlement in the property. Please note that my father has not put any money in purchasing the property, but he is the only one alive for the property. They have put all the points in the case citing examples of HUF to claim equal share of property, but we have not registered as HUF. Please let me know if remaining 3 brother have any legal entitlement in the property? what kind of proofs, we should submit to prove that we are not part of HUF and independly living since the property was purchased.