Is it permissible to lie to the brother of a deceased person and claim to have seen the deceased in a dream, pleading for help in settling his debts, in order to pressure him to pay his deceased brother's debts, knowing that he refuses to pay them despite having sufficient funds to do so?

The brother must repay the debt of his deceased brother, for "the soul of the believer is suspended by his debt until it is paid off." The debt of the deceased takes precedence over the will. If advice is ineffective, and lying is permissible to reconcile disputes, it is better to use allusions (euphemisms).