17 Rule 17.
Parties plaintiff and defendant.
Every action shall be prosecuted in the name of the real party in interest. A minor or an insane or incompetent person who is a party must appear either by a general guardian or by a guardian ad litem appointed in the particular case by the court in which the action is pending. A guardian ad litem may be appointed in any case when it is deemed by the court in which the action or proceeding is prosecuted expedient to represent the minor, insane or incompetent person in the action or proceeding, notwithstanding that the person may have a general guardian and may have appeared by the guardian. In an action in rem it shall not be necessary to appoint a guardian ad litem for any unknown party who might be a minor or an incompetent person. When the minor is plaintiff, upon the application of the minor, if the minor is of the age of fourteen years, or if under that age, upon the application of a relative or friend of the minor.