Regarding Monetory Matter

My father died in 2018 and had a bank balance. What my brother and the bank did, transferred the amount to my mother's deposit account and made my brother as the nominee. I want to know can I claim my share as there is nowhere my name in deposits neither as a nominee. In some account, my mother is nominee so the amount has been transferred to her account. In account where my mother is not nominee what bank did take an undertaking signed by me to allow my mother to have that deposit amount. What should I do in this case? Please suggest? Thank you.