Partition family joint property

My grandfather's 1989 registered will divided his property among his three sons. Critically, it stipulated that upon the death of my unmarried uncle (Chacha1), his share would pass to my brother and me. Chacha1 passed away approximately 25 years ago. My other uncle (Chacha2) sold his share of the property long ago and is not relevant to this case. My father and Chacha1 lived with us as a joint family. Following my father's death in 2022, my brother filed a partition suit against my mother an