Joint ownership involves more than just one person.  With this in mind, the name record entered for a joint owner should be designated an Organization.

When entering a joint name, enter it last name first, such as "Smith, John and Mary."  That will make it easy to look up in Advisors Assistant by last name.

This will not affect the address, since the address record has it's own addressee, and you can show the addressee as "John and Mary Smith."