A trustee is obliged to keep the orphan's social security money and not to repay the deceased's debt from it
It is obligatory to keep the social insurance paid to these orphans by the government and to support them from it, likewise their father’s pension. It is not permissible for you to settle their father’s debts from this money until they reach full legal age and approve of this. If you repay your brother’s debt from your own money, you will be a good doer and you will be rewarded for it. You can also mention them to some benevolent people, and maybe they will help to repay them and you will be assisting in something good. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.