Doubt in New Applications - Please urgent help required

[flyingbird]

As everyone knows that CIO has implemented some more application forms for the immigration. The below are the list of new applications

1)   IMM0008DEPENU  - Additional dependents declaration forms
2)   IMM0008ENU_2D – Generic Application form for Canada
3)   IMM5409E – Statutory declaration of common –law Union
4)   IMM5604E – Declaration form non accompanying parent guardian for minors immigrating to Canada. 

I was trying to fill the all forms by myself and I got jammed due to the following doubts.

My Question is related number 3. IMM5409E – Statutory declaration of common –law Union, what is this form, whether we should filled out or not because as per check list, this one is not included in checklist.  Is it applicable to an applicant , please clarify.