In Immigration Refugee Protection Act (IRPA), nowhere is it written that one cannot claim points for experience earned in father's / relative's company but that said the onus falls on you my friend to prove that you actually work for your father and that you are being remunerated by payment or commission (yes they accept commission also and for matter of fact cash salary also, as long as you can prove it) and that you are not faking the papers to claim your work experience.
Now back to onus part, provide the following documents:
A) Very Important:
1) Reference Letter.
Watch Kubeir Sir's video.
2) Salary Slips. Now because you work in family business provide salary slips for the entire work duration you are claiming points for.
3) Bank Account Statement of the salary account (again for the entire duration).
4) Tax Returns (entire duration)
5) Appointment / Offer Letter.
B) Provide if you have it:
6) Promotion Letter
7) Appreciation letter by any client
8) Any documents under the sun which supports your claim.
Follow the above mentioned, do further research (also refer to Kubeir Sir's videos on related topics) and you will be through.