He borrowed money and the person to whom it was owed has died, and he does not know how to repay it

My husband’s father borrowed an amount of money before 1948, but he did not have enough money to pay it back, and the person whose money it was died.  Then disaster befell Palestine and we were expelled from there. His financial position remained bad, then my husband’s father died, and my husband’s and my financial position was not good. Now my husband and I want to pay off this debt, knowing that we have been living in Saudi since 1967 and I do not know anything about the heirs of the man who lent the money. My husband has a brother who is out of work and has a family and handicapped children; his eyesight is very poor and he cannot work. So should we give this money to my husband’s brother with the intention of repaying this debt on behalf of the person who has died, and the charity will be on behalf of the one to whom that money belongs? Please advise me, may Allaah reward you with all good.