Here are the instructions on who needs to fill what forms:
http://www.cic.gc.ca/english/information/applications/step-by-step.aspAdditional Dependants/Declaration Form (IMM 0008DEP)
Who must fill out this application form?
This form must be completed by:
You, the principal applicant on behalf of each of your dependant.
Dependant(s)
You, the principal applicant must answer each question on behalf of each of your dependant(s). The questions are the same that you answered for yourself and other dependants on the Generic Application Form for Canada (IMM 0008).
Follow the previous instructions to help you answering the questions for your dependant.
Consent and Declaration of Applicant
Read all of the statements in all sections carefully and then:
Write your name in the space provided.
Check the appropriate box to indicate if you agree that the information contained in this application related to your intended occupation, education and work experience may be shared with prospective employers in order to assist them in hiring workers.
Sign and date in the spaces provided.
By signing, you certify that you fully understand the questions asked, and that the information you have provided is complete, truthful, and correct. If you do not sign and date, the application will be returned to you.
Note: If you are less than 18 years of age, your form must be signed by one of your parents or a legal guardian.
I'm sorry I misunderstood and gave incorrect instructions. You only need to fill out IMM008DEP if your mother has more than 5 dependants and couldn't fit them all on IMM008.
