However, minors cannot sue another person (or defend himself against another lawsuit) on their own. A minor needs help. A minor must sue or be sued through the help of a 'guardian ad litem.' (See Arizona Rule of Civil Procedure 17 (g-i)).

A guardian ad litem is a special guardian appointed by the court to represent the minor. In many cases, the minor's parent can be the guardian to do this. The guardian's role is to make sure that the minor's interests are expressed during the lawsuit. Generally, the child is the actual party named in the lawsuit and not the guardian.

So yes, with the help of a guardian ad litem, a minor can sue another minor or another adult.