How to claim property and assets after mother’s death?

There is a property in my mother’s name, and it was under bank mortgage for 26 years with her as the owner and me as the guarantor. This year, my mother passed away without writing a will. We are two brothers: Myself – married, with one 9-month-old son and my elder brother – unmarried. The property was purchased using money received by my mother from the sale of her inherited share from her mother's property, and my contribution from my business. All related payments (legal, bank charges, advance, tehsil, patwari, etc.) were made by me alone. Now, my elder brother is creating issues and wants to sell the existing house to claim his share. He and my mother’s younger sister conspired to prematurely close all of my mother's FDs and bank accounts, naming my brother as the nominee, after my mother was diagnosed with Stage IV GB cancer. They slowly transferred all the funds, and in December 2024, my aunt also took 9 tolas of gold and ₹1.70 lakhs in cash. We have a call recording regarding this. Now, she refuses to return any of it.