Hi,
page 9:
http://www.cic.gc.ca/english/pdf/kits/guides/5551E.PDF
B – My Family Members
You must give information about your family members. Family members are your spouse or
common-law partner, your own dependent children or those of your spouse or common-law partner
and the dependent children of dependent children. A common-law partner is a person of the opposite
or same sex who is currently cohabiting and has cohabited in a conjugal relationship with you for a
period of at least one year.
Dependent children may be your own children or those of your spouse or common-law partner.
So your mom is not a "family member".