Yes- as long as it falls under the NOC that you are applying for, it will count. So, for instance, if you are applying to Canada as a Factory Manager, and your work in your father's company was also in that capacity, you can use this work experience to count towards the total requirement for Express Entry.
You will need all the required documents- signed letter of reference on company letterhead, pay stubs, etc.- but it can and will count.
If this does not meet your primary NOC, you can still include it in your employment or personal history, but you cannot use it to accrue CRS points, not without changing your NOC to match your work at your dad's company.