Grouping Taxonomy terms by their parents
Hope I'm not too late, but maybe others will find this helpful...

If I'm understanding the question correctly, this is what you do:


Add two taxonomy name fields to your view display—one excluded from display, the other not.
Add a relationship of "Taxonomy term: Parent term" (under Advanced) and then attach it to the field excluded from display.
Under in the view's format settings, group by the excluded field with the relationship.


Note: If the parent terms are being printed twice (not just as group headers), make sure you excluded the field with the relationship and check "Require this relationship" in the relationship settings.

I don't know if this works with tertiary+ levels. Probably not. In which case there's most likely a module.