If I have one domain name, is it possible to cross reference what other domains the registrant may have?
Not sure I understand the question. Have you lost records on domains that you own?
If you're referring to domains that owned by others, I think not. Not through the registrar. As far as I know there is no registrar that allows queries by technical, billing, or administrative information.
Not to say that is the only way to determine the domains any one owner has...
