You first inform the bank to stop payments on the cheques if presented for payment by the complainant.
If your brother has taken loan then why do you give your cheques for payment?
You can lodge a complaint before the higher police officer about this atrocious act of the police at the instance of a third person and seek his intervention.
Make sure that you have never stood as a guarantor to your brother for his loan.
You can inform police to initiate steps to recover the loan amount from your brother and not from you.
You can approach a lawyer to issue a legal notice to the concerned police about their illegal activity unleashed against you and demand the return of the cheques from the person who made this complaint.