About synchronizing backups, I've been using this for years:

Second Copy
Automatic backup software - secure data with Second Copy

Requirements: Works with Windows XP/2000/2003/Vista/7/8/10

Purchase Information: Shareware: Free to try, $29.95 one-time payment if you decide to keep it.

Second Copy is the perfect automatic backup software designed for Windows XP and above. It makes a backup of your data files to another directory, internal or external hard disk or to a computer across the network. Second Copy monitors the source files and keeps the backup updated with new or changed files. It runs in the background with no user interaction. So, once it is set up you always have a backup of your data somewhere else.

No relationship other than as a customer.