Should your family member's device require password, and now has an
Activation Lock; to free up the device legally and remove that Lock, you
may need reason to believe there still may be useful information on it.
By reading again, more than once, I cannot tell where you are with that.
How to request access to a deceased family member's Apple account - Apple Support
//support.apple.com/en-us/HT208510
Depending on the path the device has been through, IF that was erased;
[by now] there's nothing to left to access. To acquire further access now
wouldn't get you any files from the device, IF it's already been erased by
an Apple tech. I doubt an official Apple presence did it without explaining.
So depending on what was done, and if done correctly to gain access
to the original user's account and its data, would require certain steps
followed. Otherwise someone may only unlock the Activation Lock; but
in the meantime, has then erased the content; it's not accessible now.
The above article link, tells of certain methods and if not able to follow
them in one way; by default another pathway only allows a subsequent
user to set the device up as new owner, with original data lost.
[Encrypted mail within Apple Mail, may or not, have been accessible
outside a Mail application; perhaps from the server, with password.]
https://duckduckgo.com/?t=ftsa&q=how+to+access+activation+lock
+on+deceased+apple+product&ia=web
So I believe you are now seeking an impossible path; unless you travel
back in time and have your relative provide written instruction to court;
Then after their passing, access may be gained to the intellectual data
intact. ~As it now is, that does not seem to be possible.
Instructions are clear, two ways; either you do it by one, or the other.
Maybe someone else can read the Apple article details and look for
some workaround; but I see that as missed opportunity; years ago.