Whenever a ward, for whom a guardian of the estate or of the person and estate has been appointed, is interested in any suit or proceeding in the probate court, such guardian shall in all such suits or proceedings act as guardian ad litem for such ward, except as to suits or proceedings in which the guardian has an adverse interest. Whenever a minor or other person under legal disability, for whom no guardian of the estate or of the person and estate has been appointed, is interested in any suit or proceeding in such court, the court may appoint a guardian or a guardian ad litem. In a suit or proceeding in which the guardian has an adverse interest, the court shall appoint a guardian ad litem to represent such minor or other person under legal disability.