Legal Question in Medical Malpractice in North Carolina

Generally speaking, the claim is that of the child. The parents, however, have a "derivative" claim for their medical bills (i.e. incurred to treat the child), up until the child reaches 18 years old. The child has the remainder of the claim, which consists of the child's pain and suffering,k scarring, loss of income (after age 18), and medical expenses after age 18. If the child sues, and the parents do not, then the parents claim would be barred (because it is a derivative claim and the underlying claim is extinguished). I do not know whether the parents can sue without the child, but I tend to think that they cannot; i.e. they must bring the child's claim with the parents' claim. (In other contexts, I know that the derivative claim must be brought with the underlying claim.) As a practical matter, I cannot imagine the parents suing without joining the child, through a "guardian ad litem."