Having multiple backups, on unconnected systems, is the general rule.

Whether this is done in a chain (backing up the backups) or as multiple transfers from the sources is an implementation decision: ideally the latter as otherwise a break in the first backup system can stop the second updating, but this may require notably more resources at the source end so compete for those resources with production systems so the former isn't always a worse plan.

More importantly: test your backups. Preferably in an automated manner to increase the change the tests are not skipped, but have humans responsible for checking the results. Ideally by doing a full restore onto alternate kit, but this is often not really practical. A backup of a backup is no extra help if the first backup is broken in a way you have not yet detected.

Two is one, one is none.

More importantly: test that you can restore from backup. If you're not confident that you can restore from backup, you don't have a backup.

3 - 2 - 1

3 backups

2 media formats

1 off-site