Relationships not available on household imports
We are having the same problem with relationship imports that have custom subtypes.  Our subtypes are Individual - Student and Organization - School.  The relationship is Student of (Student) - Student for (School).

The relationship does not show up for mapping during import.  My testing shows that it's the first part (a) that causes it not to show up.  If the (a) is changed to Individual it will show up, all other combinations do not.

I have also verified that this relationship does show up in 4.5.4.  This is the only 4.5.x version I could readily test with.  I have verified on the demo test as well.

I have created an issue: https://issues.civicrm.org/jira/browse/CRM-17544