Does the debtor remain obligated to repay the loan to his brother, despite his declaration of bankruptcy and the court's approval of his request, and the consequent disallowance of anyone to claim any debt after the judgment is issued, given the debtor's knowledge that his brother had listed the loan as part of his losses to obtain a tax deduction?

Whoever borrows money must repay it, whether it was an interest-free loan (qard hasan) or an interest-based loan (ribawi). Repentance is obligatory for an interest-based loan, for Allah commands the fulfillment of trusts. Declaring bankruptcy and a court ruling to that effect do not nullify debts unless their owners voluntarily relinquish them. These debts remain the responsibility of the debtor until he is able to repay them. It is recommended to grant the one in hardship a delay or to waive the debt for him. However, if the creditor does not waive his right, the debt remains binding until it is paid, and a court ruling does not invalidate it.