Ahoy there, Karen! Welcome aboard planDisney! I see you're just a few days from setting sail so let's get right to it without delay! Especially since there are important details to take care of between now and Friday!
It's important to remember that the My Disney Experience website and app are only used for your Walt Disney World Resort vacations! When it comes to Disney Cruise Line, the two most important things to take care of before are your
Online Check-in which can be done by anyone with access to the reservation for the entire sailing party, assuming that you have all the required travel documentation on-hand. If your brother is on the same reservation as you've made it sound, you should be able to check him in just fine.
When it comes to Safe Passage, that system is separate and doesn't require a Disney Account to complete. Specifics about uploading test results and current requirements can be found in the "Know Before You Go" information on the Disney Cruise Line website, but the good news is as long as his name, birthdate, and reservation number match what is on the booking, he should not need any additional access to create his Safe Passage profile by clicking the "Register New Guest" button on the
Safe Passage site.
If it were me, I'd ring up your brother and be sure he has the right reservation number - and maybe remind him about the current testing requirements!
I hope that helps you set your course for smooth sailing over the next couple of days, Karen! Thank you so much for your question, and if you have any others - even with the short time before you embark, you know where to find us at planDisney!
Fair winds and following seas!
Andrew