About what I do. In my home directory on my computer, I have one directory called "Zarchive" where I put all the stuff I want to keep. (I called it "Zarchive" because it is a French pun. I keep "mes archives" in it.) The other directories in my home directory are symbolic links/shortcuts linking to directories in "Zarchive" or they are things I do not care to lose.
To organize things in my special directory, I first used Johnny.Decimal. Then, I got rid off the decimal prefixes because I am the sole user of this file hierarchy.
Here is a summary of the directory organization in this directory. I did not put all the directories but you get the idea.
.
├── index.txt A file explaning what each directory are for.
├── Configuration Conf for my PC (dotfiles, scripts...).
├── Knowledge My notes.
├── Media Things I keep but I could find online or in store.
│ ├── Books
│ ├── Games
│ └── Videos
├── Personal All things that are personal (pictures, GTD...).
├── TODO Things I should do one day (
│ ├── 2024-08-17 Articles to read
│ └── 2024-08-17 Phone pictures
├── Various Things that I do not know where to put.
└── Work Anything work related (personal or professional)
├── Companies
├── Employment
├── Freelance
└── Projects
Maybe I could do a full blog post on my file organization and its management if you want.
Anyway, to get back on your topic. If I were you, I would put all the files you mentioned in the directory "Personal". Now for your example for the eye doctor: or you could create a directory "2024-09-26 Eye doctor appointment" with everything in it; or you could have directories named "Receipts" and "Health", and in Health you have a symbolic link/shortcut to the receipt in Receipts; or you could have a copy of the receipt in both directory. I prefer to make each directory independent, so I am not fond of the shortcut solution.
For your family member's files, you could have a directory for each of them. Maybe you could create a directory "Family" in the top directory and each member is responsible for his or her stuff.
With that said, it does not completely remove the need to search for files. Yes after doing that you are now organized with a good file hierarchy, but that does not mean you cannot use a good tool for finding files. I do not have much suggestion on this domain because I am lucky enough to be good at remembering where I put stuff. Most of the time... :)
As a final word: I really encourage you first to read Johnny.Decimal, then to really take the time to define the areas and categories without rushing, then to organize the files, and finally to use the search tools. Some people say that you do not need to organize anything and that you can rely only on the search tools but I completely disagree. Tools are not available forever, and it does not solve the issue of syncing correctly your files and archiving them.
I hope I was clear. I did not expect rambling so much when I started to write this post. Good luck for organizing your stuff!