We pick d.root-servers.net, one of the 13 root servers (1), and ask it about ns1.dns-servers.info and learn that info is delegated to six name servers (2), so we ask d0.info.afilias-nst.org where we learn that dns-servers.info is delegated to two name servers, including ns2.dns-servers.info (3), so we ask that one and get the following answer:
All of the seven domains that use the primary name server ns3.system0.net use name server group 1 (example: kevinmuldoon.com, system0.com and system0.net ). Worth noting is that seven of the domains that use name server group 1 use the primary name server ns3.system0.net.
The two name servers ns3 and ns4.system0.net together
There are about twenty domains that use name server group 1.
All of the three domains that use the name server ns1.dns-servers.info use the two name servers ns1 and ns2.dns-servers.info together, hereafter referred to as "name server group 2".
The two name servers ns1 and ns2.dns-servers.info together
All of the three domains that use name server group 2 use the primary name server ns2.dns-servers.info.