What are the options for updating Old registered partition deed based on New construction?

Dear Lawyers, Good afternoon. We hold a joint property and have recently constructed a new one by demolishing the old structure. The old partition deed says GROUND FLOOR belongs to elder brother and first floor belongs to the younger brother. In the revised scheme of things based on the New construction, there is no GROUND FLOOR and FIRST FLOOR and instead there are FIRST FLOOR and SECOND FLOOR. Going forward, based on the new construction, we would like to update the property document separately as follows. The FIRST FLOOR / FLAT belongs to all the legal heirs of ELDER BROTHER and the SECOND FLOOR / FLAT belongs to all the legal heirs of YOUNGER BROTHER and the rest of the NON UDS is COMMON to all the legal heirs. Both the brothers died interstate. Based on the above, kindly advise what are the best and simple options available to update the property documents and that will help towards separate property tax assessment, EB, Water, Sewerage separately for both the floors?