Petition for letters of administration must be in writing, signed by the applicant or his counsel, and filed with the judge of the court stating the facts essential to give the court jurisdiction of the case, and when known to the applicant, he must state the names, ages and residence of the heirs of the decedent, and the value and character of the property. If the jurisdictional facts existed, but are not fully set forth in the petition, and are afterwards proved in the course of administration, the decree or order of administration and subsequent proceedings are not void on account of such want of jurisdictional averments.