The short answer is no.
Our auto insurance products are designed as a 3 way relationship between you, your cell phone, and your car. If you were to create a second account for a 2nd car with the same email and same cell phone, you will find that the trip detection function will start confusing the miles between the accounts, the automatic top-up financial functions will start applying money's incorrectly, and electronic communications may get sent to the wrong account for the wrong reason.
The best course of action is to have the driver of the second vehicle create their own account with their own email address and cell phone number. That way, you will both have your own vehicle's assigned to you and the trip detection, financial transactions and electronic communications will be sent to your respective emails and cell phone numbers.
Simply have your family member download the App and set up their own Just Insure account with their own email address and their own cell phone numbers and vehicle information. Rest assured that you can both drive either car and be covered as long as they are a licensed driver!
Whether you have the "Per-mile" or "Unlimited miles" insurance policy, we hope you will see the savings that our other customers are seeing.