In order to generate two report cards for a student, the student must have both parent addresses attached to his/her contact card and have the "Mailing Address" check box selected for each of those addresses.

To specify Mailing Address for each address: 
  1. Core
  2. Users Edit User Profile Data 
  3. Search for the User 
  4. Scroll down to the Address block
  5. Select Edit
  6. Select the Mailing Address check box. 
User-added image