Nominee discrepancy

Sir. Good evening. I seen us valuable advice. My brother has fixed deposit of 50000 in Karnataka bank. My brother died in 2015. His policy is matured on 8.1.2018 and it automatically renewed till 7.1.2019. He mentioned his friend as a nominee to that fixed deposit and savings account. We don’t have fixed deposit receipt and account passbook with us. Yesterday I met bank manager n open up my brother deposit opening application form.  In that there is only nominee name is present without his contacting details and mentioned the relation as cousin brother only. But he is not our relatives. He ìs only friend to my brother. Manager told me that they have to give matured amt to nominee only according to bank rules. And also suggested to bring legal heir certificate so that they can send them to higher authorities to decide. Please comment on this issue. Meanwhile if nominee came to bank to claim amount before I produce legal heir certificate to bank..what I have to do.. because manager says money be given to nominee. Any problems we have to face with the nominee and with branch manager in taking my brother fixed deposit amount. As myself and my father are legal heirs shall we claim that amount. Please clearify sir at earliest. And also pl let me know who has to issue legal heir certìficate whether neo or court. I am confused and legal heir certificate and letter of succession. Thanking Ramkumar