Final answer:
The holder of a Probationary Driver License under 21 is typically allowed only one non-family passenger under 21, but it can vary by state law.
Step-by-step explanation:
The number of passengers that a holder of a Probationary Driver License (under 21) is permitted to have in the vehicle excluding dependents can vary based on state laws. Generally, during the initial phase of the license, the driver is allowed to have only one passenger under the age of 21 who is not a family member. However, this rule can differ depending on the state, so it is crucial to check the specific driving restrictions of your state's Department of Motor Vehicles (DMV).