Haw. Rev. Stat. § 551-2

Nothing in this chapter impairs or affects the power of any court to appoint a guardian to defend the interests of any minor or person not in being impleaded in such court, or interested in any matter there pending, or its power to appoint or allow any person as next friend for a minor, to commence, prosecute, or defend any action or proceeding in the minor's behalf; provided that in all proceedings for annulment, divorce, or separation, except in the case of annulment on the ground of nonage, either spouse, although a minor, may sue or be sued in the minor's name without a guardian or next friend.