Generally, the waiver of notice is used to avoid giving notice to other interested parties over time. If your brother refuses to sign the waiver, then he is entitled to notice as set by statute. Your intent to do what is right does not reduce his rights in the estate. If you are willing to become the personal representative, you should contact a local lawyer and petition the appropriate court for letters of office. As part of that process, you are likely to be required to provide notice to your brother (and any other party who is entitled to notice and for whom you do not have a waiver on file). Typically, your brother will have an equal right to request appointment as the administrator or personal representative. If he asserts this right, the judge may appoint you as joint administrators. Although this is not a great working result, it may be the result required by statute. You really should see a local lawyer today to get answers to this question.
A Waiver of Notice is designed to streamline the process of appointing an estate representative. It is not required however. Each next of kin/beneficiary is entitled to notice taht an Application for Appointment has been filed. The Court needs to set the Application for hearing. If an individual is not willing to sign a waiver, then the Application is set for hearing and the individual must be given a notice (usually by certified mail) of the date, time and place of the hearing. That individual is then free to show up at the hearing and object to the appointment. If he/she does not show, then the Court can proceed on the Application.
Here in Maryland, the Waiver of Notice can serve multiple purposes. Typically, a party waives the right to receive notice that a personal representative has been appointed in the estate (and thus saves the estate the cost of certified mailing of such notice).
The form that is used in Maryland, RW1101, allows the person waiving notice to waive other notifications from the Register of Wills, such as Notice of filing the required administration account(s), Notice of the payment of attorney's fees and personal representative's commissions, and more.
A person who signs the Waiver of Notice can revoke the waiver, provided they serve that waiver on the personal representative.
Disclaimer: This answer does not create an attorney-client relationship, it does not constitute legal advice, and it should not be relied upon as such. Laws vary from state to state, and an attorney cannot fully evaluate your situation without a comprehensive consultation and review of all facts and information readily available.