If a guardianship was obtained by filing false information and intentionally not signed under penalty of perjury or giving both parents notice of guardianship hearing until 9 months afterwards but filed a proof of service without the date actually served to intentionally deceive the court into believing parents were notified prior to the hearing and just didn't show up to contest the guardianship is there anything a parent can do to terminate this?
it is always possible to challenge appointment of a conservator on various grounds, including the fact situation you have described (upon sufficient proof). you will need to retain a qualified attorney to provide you with specific advise and represent you (or the conservatee) by filing a petition with the superior court.