How to claim deceased father's property without nominee?

My father passed away on August 1, 2020. There is no nominee registered in his bank account. My mother, who is 67 years old, is his legally wedded wife and surviving spouse. She is his second wife. He is survived by two married daughters from his first wife and two sons and five married daughters from my mother. All the children live in different parts of India and are not on speaking terms, except four of them. We are Hindu by religion. What is the best way to claim the unclaimed money lying in the Indian savings bank account? How long will it take, and what fees are applicable? The amount is around ₹40,000.