If you come from a family filled with professional electricians, you've likely learned pretty much all there is to know about electrical work. In fact, you may have helped your family members with their businesses. If you want to strike out on your own, you certainly have the field experience to do so -- but you should still get an electrician certification. Studying toward a certification does not mean that you learned very little outside school; it means that you have decided to ensure that your knowledge is well-rounded and extensive so that your future customers know they can trust your work.
New Customers and Your Reputation
Your family's current customers know your name and your family's reputation. But new customers, and people who live outside the service areas that your family's businesses work in, won't know who they're really hiring unless they can see evidence of your knowledge. If you have an official certification, your customers will know that you have at least a basic level of knowledge and they can trust you to fix most electrical problems. Word of mouth from previous customers to new customers helps somewhat, but it's that official piece of paper that's going to show you aren't a random person claiming to be an electrician.
Law Updates and Regulations
Another advantage to going to a trade school and officially studying to be an electrician is that you'll learn the latest regarding laws, regulations, technological advances, and conservation techniques. Electrical technology for both home and commercial applications is expanding and changing rapidly, and trade school is one of the best places to find out about new techniques and materials being used in electrical systems.
If you live in or are moving to a state that requires certification to get licensure, or if your bond insurance company has told you that you need certification to be approved for a bid bond, then you really do need to go to trade school and get that certification. You might be able to find a school that offers a test to skip classes and get the certification anyway, but then you'd miss out on all the other benefits of getting formal electrical training.
Electrical programs don't take that long to complete, but the rewards last a very long time. Start looking into trade school certification programs now so you can start your own electrician business as soon as possible.