Is it a law that your child has to be twelve years old sit up front in car?

No, there is no such law in the United States that requires a child to be twelve years old to sit up front in a car. However, some states have laws that require children under a certain age or height to be in a child safety seat or booster seat. These laws vary from state to state, so it is important to check the laws in your state to make sure you are following them.