Patta is in my Dad name

Hi , I am Pelsia Rani. My Dad has property in tamilnadu. The property patta is in my Dad name from year 1984 but the property tax was paid in my grandfather name (i.e Dad name) who was passed away in 1983. My grandma had taken light bill and water bill also in my grandpa name. My dad have two sisters who had stolen the original document after my dad death at 2016 and my grandma also died on 2017. Now they are saying they have rights on the property. We have only the online patta document where it mentioned my Dad is the land owner. Kindly suggest me whether i can win based on the patta document. Summary of the issue: 1981 - Land was brought by my grandpa 1982 - House was built 1983 - grandpa passed away 1984 - In patta my dad name was present as land owner. From which year i dont know but till last year property tax was paid in grandpa name by my grandma. Now my dad and grandma both passed away Now my grandpa two daughters saying its their dad property so they have rights on it. Kindly help me to tackle this situation. Please..!!