For return back original documents from bank after completing home loan.

Hello Sir/Madam, my name is Praveen Shukla, my father took a home loan from ICICI bank in 2007 and my big brother in co applicant in this loan, after one year my father died (2008) because of heart attack, after death i tried from bank to revers the loan than they said to me your father (main applicant) is not cover in insurance and they cover co applicant my brother in insurance. that why we need to pay whole loan amount after death of my father. so we done as bank said to us we paid all loan amount and also dues which created after fathers death. in December 2018 we done this loan. after completing loan when we ask for return back registry and all original document which they have, they denied to return to us either co-applicant they asking for succession certificate from court. we ask them why we need succession certificate if co - applicant is available and also he repay all loan amount. when i go to the court for succession certificate the advocate told us court will take 5% stamp duty for creating this certificate. and property cost in this time is approx 40lack and 5% its approx 200000 and its very big amount for us to pay. we are very confused what should we do. please help us from your knowledge. and i want to know of rights of co applicant, thank