Education loan interest waiver

Please help me in knowing how to approach bank to seek education loan interest waiver in One time settlement. We are unable to pay loan amount 13 lakhs plus Interset added up to 7 lakhs since 2008. My brother took loan in 2008 for education loan under cent vidyarthi loan scheme in central bank and he didn't got job in London after studies and not able to pay the emis and it became a huge burden for my parents and we gathered some money after my mothers retirement and approached bank for onetime settlement. Now we want to know how much interest will be waived off under one time settlement and we want to pay very low and bring the relatives collateral back from the bank which is under bank since many years. Please help us.