The property tax bill could be changed in your name if the land records with the municipal corporation show you as the owner if the property is held in your name with the corporation than this can be changed just by way of a simple application.
From the above, it appears that property has been owned Shri Vinod and his sister, but ownership has been done through registry or power of attorney - not known; property is free hold or lease hold - not known. If we assume that registry has been done and property is freehold than `Mutation of porperty ` has not been done by Shri Vinod and his sister. Mutation of property means the recording of ownership in concerned developments authority`s or corporations office. He may approach the concerned office to know the procedure which includes submission of desired affadavits duly notorised, publishing in national and local newspapers, submission of fee for transfer of name in the authority`s office etc. The exact procedure can vary from state to state. But this should be done by the new owners of property at their earliest in their own interest.