Pension for Widow

Hello My father was an employee of SBI. He died during service on December 10, 2018. He still had 4.5 years of service left. He was an employee of State Bank of Patiala before the merger in April, 2017. During the merger all the employees of the associate banks were given an option to choose between the benefits of SBOP or SBI. My father has verbally told us that he has opted for the SBI benefits. We do not have any written proof of it. And the bank has also lost those documents as were told by the bank. So when my father died in the absence of any documentary proof the bank has given us the benefits of SBOP. That is fine with us so far. The only issue is the pension because we have been told by many people including friends of my father who are still working in the bank that in the benefits of SBI till the time my father's age reaches the age of retirement we will receive the full pension and after that we will receive the family pension. But nobody has been able to provide any written document confirming this. The same has been said about the pension in SBOP that we should receive full family pension till my father's retirement age. So what I need from you is what are the rules of pension in both SBOP and SBI. Any circular/notification from bank, RBI, Finance Ministry, GOI etc. in this matter. And I need the source as well. Please let me know your charges. I will deposit the money into your account in good faith before you start working on this matter. I do not live in India so the whole communication has to be done via email. My email id : [deleted] Please give me your email address as well. Kind Regards Abhinav