I cannot reproduce your findings, I see a lot more information in the results for the whois queries, for example a list of "domain servers" for amazon.com: PDN

I cannot reproduce your findings, I see a lot more information in the results for the whois queries, for example a list of "domain servers" for amazon.com: PDNS1.ULTRADNS.NET PDNS2.ULTRADNS.NET PDNS3.ULTRADNS.ORG ... and so on ... Or "domain servers" for paypal.com: ns3.isc-sns.info ns2.isc-sns.com ns1.isc-sns.net So maybe the answer to your question is yes, a whois query can return results with subdomains of other domains having the query domain as a prefix, if this subdomain is listed as a "domain server". But the result you have posted above really looks quite different from what I see, there seems to be (or have been) a problem.