Wis. Stat. § 879.13

If for any reason notice to any person, including a minor or incompetent, is insufficient, the court may at any time order service of notice together with documents required under ss. 858.03 and 862.09 and, where required, appoint a guardian ad litem under s. 879.23 and require the person or the person's guardian ad litem to show cause why the person should not be bound by the action already taken in the proceedings as though the person had been timely served with notice. Such person may consent in writing to be bound.