Comment More than Debian and Fedora/Red Hat (Score 1) 110
- Slackware has spawned lots of distros (including SUSE)
- Enoch spawned the Gentoo line of distros (and Gentoo is the current base of ChromeOS).
- The Arch family started independently
- The on-the-rise Alpine Linux was independently started
So by lineage alone I'd argue there are more than two major categories.