I advise you to contact them, which i did few days ago. Below is their response for your info.
If you are the principal applicant of a permanent residence application already in process, you could add your spouse or common-law partner, dependent children, and their dependent children to your application, even if they were listed as a non-accompanying dependant in the initial application.
To do so, we invite you to send your add-on request through the IRCC webform available on our website. You can attach the following forms and documents in the field reserved to that effect:
- A new Generic Application Form for Canada (IMM 0008) with supporting documents,
- (If applicable) A Schedule A - Background/Declaration (IMM 5669) form,
- (If applicable) An Additional Dependants/Declaration (IMM 0008DEP) form,
- (If applicable) A signed Additional Family Information (IMM 5406) form,
- A copy of the birth certificate, marriage certificate or proof of common-law relationship,
- A copy of the family member's valid passport,
- Police certificates for all countries where the family member over the age of 18 has lived for more than 6 months since turning 18,
- A letter of explanation, and
- If applicable, the proof of payment.
- If you need information to fill out the forms, please consult the Fill out the forms section of the instruction guide found in the application kit that you have initially used to apply.
- If the newly eligible family member is a spouse, common-law partner or dependent child who is already a permanent resident or Canadian citizen, only a copy of the birth certificate, marriage certificate or proof of common-law relationship and a letter of explanation are required.
- It may be impossible to add a member of your family to the application if a final decision has already been made.
