Canada Visitor Visa - should I mention working in a family business?

I am not familiar with the specific forms that you must complete to apply for a tourist visa to Canada. But it may be useful to know what IRCC (or any other visa-granting authority) is looking for.

Any country evaluating a visa application is assessing whether the applicant is telling the truth in the application, can afford the trip, and is a person who will obey the terms of any visa or entry permission. The most important part is assessing if the applicant will leave when the visit term expires, and not overstay.

You should complete the application truthfully.

The application will seek identification information and a recitation of your travel history. Canada shares immigration information with the UK and the United States, so whatever information those countries have will also be known by IRCC. If IRCC sees inconsistencies between what you state in your application, and what you might have previously stated to another immigration authority, or what IRCC discovers if it conducts any independent fact-gathering, the inconsistencies will count heavily against you, and may by themselves result in a denial.

The will-the-applicant-leave-afterwards question is significant. Previous international travel with no overstays is a positive indicator. Even more powerful are connections to your home country (or your country of usual residence, the UAE) which will draw you back there after your visit to Canada. A marriage partner, a child, ownership of real property, and continuing steady employment to which you must return are positive factors for a visa application. If you work in the family business, then of course you should mention it.

The business information presented to the the UAE government - that it is your aunt's business — may not the truth: the business would be more accurately described as being owned by your father, who receives the business profits.

Thus, if you assert (or have asserted) that your aunt is the owner, you will now be admitting that you are (or have been) dishonest in your business dealings. This presents badly. Even with an explanation, these facts may be sufficient to cause the application to be denied.

Remember too that you are not required to answer questions that the form doesn't ask. You may be able to honestly describe your job or even the employer or business without going into the facts of the business' ownership.

This is a dilemma: without a job, the trip won't be affordable and there's much less reason for you to return to the UAE. Without having a job to return to, there is little hope that a visa will be granted to you. On the other hand, if there is any difference between how you now describe the family business and how the business appears to the public or the UAE government or the IRCC, it's possible that the difference may reflect badly on you.

You will have to resolve this dilemma for yourself.