A Pennsylvania Petition to Intervene is a legal document filed in the Commonwealth of Pennsylvania to allow a third party to become a litigant in a civil legal action. This petition is commonly used in family law cases to add a non-party (such as a grandparent or step-parent) to join the action and seek a legal resolution. The petition must be supported by evidence, such as affidavits or other documents, and must be filed with the court according to the applicable local rules. There are two main types of Pennsylvania Petition to Intervene: a Motion to Intervene and a Petition to Intervene. A Motion to Intervene is commonly filed when the non-party seeks to add himself or herself to an existing action, while a Petition to Intervene is used when the non-party seeks to start a separate action in conjunction with the existing action. In either case, the non-party must demonstrate a “legal interest” in the matter that is sufficient to justify their involvement.