Claim of loan from sons being legal heirs after father's death

Hello, My father died when i was 23 years old. My mom is a housewife. My father died suddenly due to cardial attack. At that time, we just knew that my father have personal loan from bank (paid in monthly instalments) and also some of his business clients owe money to him. My dad used to say mom that you will get 1 crore as an insurance amount if i die. I am not sure if that was just joke or he was serious as my mom is religious and she never took such things seriously and never wanted to live on such money. I have a twin brother who is self-employed hard working guy earning a decent living to survive with mom. We don't have any asset but living a decent living through hardwork. My question is - Are there any chances that bank could claim from us as we are legal heirs. We don't know how much is the amount and what the money has been used for as my mom was against of going for loans and stopped him. If bank officials claim from us, what action we could take and justify ourselves.