Here it is, a linux timeline. Much more accurate than the unix one I posted a while ago:
http://www.kde-files.org/content/files/44218-linuxdistrotimeline-6.8.2.png
I actually throught Suse forked off RedHat, since they're an rpm distro.
It's intetresting to note that few of the original distros are still running, in most cases needs have changed and the project was abandoned or forked with another etc. RedHat is an exception here, they founded a company around their distro and are still going strong.