You do not have to pay their fees but you do have to show enough funds to support them in case you decide to sponsor them as soon as you get to Canada.
Hello,
If you don't include your family members with your application, in future it might be a problem to bring them in Canda. just read following para copied from CIC website guide(E37048).
10. NON-ACCOMPANYING FAMILY MEMBERS DECLARATION (IF APPLICABLE):
If you have a spouse, common-law partner or dependent children and you do not
intend to include them in your application for permanent residence, submit with your
application a notarized statutory declaration stating your intention to proceed to
Canada without your family members, and confirming that you understand that your
family members must meet immigration requirements in their own right if they wish
to join you in Canada.