to make you understand:
You are the FSW Principle Applicant.
Persons who will fill the form Additional Family Information:
1. FSW Principle Applicant as main form filler + Spouse of FSW Principle Applicant
2. Spouse of FSW Principle Applicant as main form filler + FSW Principle Applicant as Spouse of main form filler
Hope that helps
Regards,
Pankaj