I think we've all done it at least once......that superseded/amended kid return will take months and months and months to complete processing, you may as well cut your loss of time now and paper file the parents.

FWIW, that's the first thing I do now when preparing a dependent return, check those 'Are you being claimed' boxes, before I even enter their name or address and get distracted!   And I still dont always trust it and I EF the parents return first!