Is it obligatory to repay a debt to a deceased person's heirs (mother, wife, and young son) when the debtor knows of the dire financial straits of their guardian and that he is spending from his own money?

The deceased's debt is considered the property of his heirs and must be paid directly to them if they are adult and mature. If they are not, it must be paid to their guardian if the conditions are met; otherwise, it is paid to the Sharia (definition) judge. It is not permissible to give money to a minor or to someone who cannot manage it properly. The minor's expenses are to be covered from their share of the inheritance.