My brother passed away and I have his iPhone and Mac but do not have the passwords. What can I do to access them?

Apple needs to see a copy of the death certificate and a copy of the will or a document that shows you inherited it.

How to request access to a deceased family member's Apple accounts - Apple Support.    

JKJ1949 Said:

"HMy brother passed away and I have his Mac and iPhone but do not have his password. How do I go about accessing them?“

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You don’t. Apple does it.

Contact Apple Support, and request support on this. You’d probably need a death certificate or sorts. Then, maybe they can modify it all.

Apple Support Contact Info:

• Contact Us - Choose Locations
• U.S.A. (800)MY-APPLE
• Proceed from there as necessary

Note: Phone calls are taking a bit to go through at the moment, due to lots of calls. With the Coronavirus Pandemic, many are at home at the moment, with much time on their hands to contact Apple. So, just stay on the line, and you will get through :)