Backing up your computer properly
A backup you have to remember to run is not a backup. It needs to be automatic, and there need to be two.
What's usually going on
Computers fail, get stolen, and have things deleted from them by accident. One copy on an external drive protects against the first. A second copy somewhere else protects against fire, theft, and the drive itself failing. Syncing services like iCloud Drive or OneDrive help, but they also faithfully sync your deletions.
Worth trying first
Set up the built-in backup.
On a Mac, plug in an external drive and turn on Time Machine in System Settings, General. On Windows, search for "File History" or "Windows Backup".
Add a copy somewhere else.
An online backup service copies everything to a secure data center automatically. It is the copy that survives if something happens to the house.
Check your photos separately.
Open iCloud Photos or Google Photos on the web and confirm recent pictures are there. Photos are what people miss most, and assume are safe.
Test a restore.
Once, deliberately, open the backup and bring back one file. A backup that has never been tested is a hope.
Leave the drive plugged in.
For a laptop, plug it in at the desk at least once a week. Backups only cover what existed the last time they ran.
When to hand it over
If you don't know whether anything is being backed up, if the family's files are spread across several computers and drives, or if you'd like someone to confirm that a restore would really work.
Your own technologist, on call.
Tell us a little about your setup. We'll take it from there.