Canada does not offer a visa application form for a group, although you can submit those of your family in the same envelope, and you can reference your friend in your supporting documentation, but not as a family member.
Can I fill out one visa application for my whole family if we are travelling together?
No. Each person must complete and sign the Application for Temporary Resident Visa (IMM 5257), as well as any other forms needed. Each applicant aged 18 or over must also complete the Family Information form (IMM 5645).
You can submit all family member applications in the same envelope with one payment receipt for the total fee for all of your applications.
Parents or guardians can help children fill out their forms. Parents or guardians must sign the forms for any children under the age of 18.
Your friend, who plans to accompany your family on the visit, would need to apply separately, but provide the same itinerary, along with the documents that support his/her application. In particular, the explanation of the purpose of travel should include information about other with whom they'll travel (your family).
And, during any interviews, that you're all travelling together would be discussed, of course.