LOA - Letter of admistration

Hi, My Mom passed away in 2019 (5 years back) and my father recently passed away 1 month back. My parents have 2 immovable properties (flats) and both are in the name of my father now and they were originally allotted to my MOM directly from MHADA Mumbai. Papa has left back a will which states House A to be given to younger brother and house B to be given to Elder brother. We don't know if its registered or not and if the will has an executor or not. Now the problems :- 1. Elder son wants to live in House A (given to younger bro as per will) 2. Younger son wants to live in House B (given to younger bro as per will) We Both bother have mutually decided to ignore the will and get a document prepared to transfer the MHADA properties in our respective names as per our above mutual understanding after consulting a lawyer. As these are MHADA properties (Lease oriented) we may have to prepare some sort of legal document, we contacted a couple of lawyers and some one asked to go for LOA and someone Succession Certificate. Now which document we should go for and can we go for this mutual understanding against the will? can someone pls guide, what we should do..?? Now as there is