I am copying and pasting from the guide and at section for
Generic Application Form for Canada (IMM 0008) Question 3
Question 3
Enter the total number of family members included in your application. This includes yourself and any
family members, regardless of whether they intend to accompany you to Canada or not.
For refugee claimants in Canada only: Enter the total number of family members included in your application for refugee protection who are with you in Canada.
Family members
An applicant’s closest relatives, in the context of an application to IRCC. It is defined as a spouse or common-law partner, dependent children, and their dependent children
SO for your case, family size is 2.