Answer:
Your question is troublesome.
An executor must be appointed by the probate court. The executor has the duty, power and authority to settle the estate under the supervision of that court. If you are the duly appointed executor it is YOUR responsibility to pay any estate taxes that are due. In fact, the debts of the decedent must be paid before any assets are distributed to the heirs. Therefore, the heir you speak of shouldn't have access to estate assets until the estate taxes and creditors have been paid. As executor you can be held personally responsible for any debts of the decedent that are not properly paid.
You should consult with an attorney who specializes in probate law.