yes debian the dad (ubuntu and knoppix ) and grandad (linuxmint easypeasy ) has just had its birthday only slackware is older in the distros that are still active and even as a slackware user i got to admit what a large and diverse family of offspring there is now
Great grandad to Peppermint … and no doubt a few others.
Though I’ve never counted them, I’d be willing to bet way over half the distro’s out there can trace their lineage to Debian … so they must be doing something right 
either debian and redhat and it wouldbe 80%ish i would think