Check list before signing Bank Forms (Nominee claims, Locker opening)

Brief:nMy Father died intestate. My mother died after few years. It's not informed to me if My mother has executed any Will. We are two married sisters, one married brother and widow of second deceased brother. My father acquired one Residential Property at Jaipur where they were staying. My deceased mother has nominated some mutual funds to me and my two sons. I don't know if succession certificate has been processed. nQ. Can bank execute nominations and allow access to locker without SC?