Your authority/responsibility continues until terminated by the court. You probably should consult with an attorney before the hearing, though. It could go bad for you quickly, and it might be nearly impossible to change the result after the judge makes a ruling.
Ms. Paquette is correct, you can continue to act until the probate court orders you to stop. Even if your younger brother doesn't have a lawyer, you should consider getting one. You could contact Ms. Paquette or me or another lawyer of your choice to help you persuade the court to allow you to finish administering the estate.
I am licensed to practice law in Michigan and Virginia and regularly handle cases of this sort. You should not rely on this answer. You should consult a lawyer so you can tell the lawyer the entire situation and get legal advice that is precisely tailored to your case.
MCL 700.3611 (1) states:
(1) An interested person may petition for removal of a personal representative for cause at any time. Upon filing of the petition, the court shall fix a time and place for hearing. The petitioner shall give notice to the personal representative and to other persons as the court orders. Except as otherwise ordered under section 3607, after receipt of notice of removal proceedings, the personal representative shall not act except to account, to correct maladministration, or preserve the estate. If removal is ordered, the court shall also direct by order the disposition of the property remaining in the name of, or under the control of, the personal representative being removed.
Be very careful. "Preserve the estate" can mean a lot of things, but you really need a lawyer if you don't have one. Definitely file your inventory, but you should not be distributing money to devisees or heirs at this time. Depending on the size of the estate and amount of liabilities owed, you may not be "in the right" in paying the debts of the Decedent. Lawyer up
This answer is intended to provide legal information, not legal advice. Legal advice should be provided by licensed attorney only after full disclosure of all facts. If you desire a no-obligation consultation to obtain legal advice, please contact me at 586-268-4463.
You can continue to administer the estate -- and probably SHOULD -- so long as you do not make any distributions that your sibling will want to challenge. So, yes, continue to pay valid bills and expenses (to anyone but yourself); make sure you have done all you can to insure or otherwise protect the estate assets. Just ceasing your duties may send the Court the wrong message.
In any case, be sure to have an attorney represent you in this matter; and contact them NOW so that they can prepare for (or ask for a postponement of) the court hearing. Immediately engaging an experienced probate attorney will allow you and your attorney to work together to either defend the challenge or, if you wish to relinquish your duties, to allow appointment of a new administrator that you and your siblings can all agree on -- or at least one that is independent from any beneficiary's personal interests. Good luck!
veRONIca jarnagin, atty, pc 317-253-7664 provides this response as general guidance and not specific legal advice. If you wish to receive specific legal advice for your situation, please call to schedule an appointment.