Your phone passcode: the six digits that hold everything
Phone makers can't unlock it for your family.
A phone holds contacts, photos, banking apps, and the security codes that unlock nearly every other account. Without the passcode, much of that can be out of reach.
Apple and Google generally won't unlock a device for family, even with a death certificate. At most, they can help reset it, which wipes what's on it.
Three things to write down
Your phone passcode
Your phone carrier account PIN (needed to move the number and receive security codes)
Where your backup codes or password manager details are kept
Good to know
Keep these on paper in a sealed envelope in your binder, not in a notes app on the same phone.