All applications to courts, except motions in matters at issue, shall be made by verified petition. All petitions must show the jurisdiction of the court and the interest of the petitioner. All petitions, except those for statutory certificates or for ex parte orders in proceedings already pending, shall also show the names and post-office addresses of all persons interested, so far as known to the petitioner or ascertainable by him or her with reasonable diligence; and shall indicate who are minors or otherwise under disability, and the names and post-office addresses of their guardians. No defect of form or substance in any petition may invalidate any proceedings.