As for "is RHEL 'like' Fedora Linux?": Yes.
ID="rhel"
ID_LIKE="fedora"
CentOS is the odd one out in this regards, as from a strictly interpreted standards POV, CentOS should have the above ID_LIKE and RHEL's should be "centos fedora". Instead we have the above and:
ID="centos"
ID_LIKE="rhel fedora"