Del. Fam. Ct. R. Civ. P. 24
(a) Intervention of right. Upon timely application anyone shall be permitted to intervene in an action: (1) When a statute confers an unconditional right to intervene; or (2) when an applicant claims an interest relating to the property or transaction which is the subject of the action and is so situated that the disposition of the action may as a practical matter impair or impede the applicant's ability to protect that interest, unless the applicant's interest is adequately represented by existing parties.
(b) Permissive intervention. Upon timely application anyone may be permitted to intervene in an action: (1) When a statute confers a conditional right to intervene; or (2) when an applicant's claim or defense and the main action have a question of law or fact in common. In exercising its discretion the Court shall consider whether the intervention will unduly delay or prejudice the adjudication of the rights of the original parties.
(c) Procedure. A person desiring to intervene shall serve a motion to intervene upon the parties as provided in Rule 5. The motion shall state the grounds therefor and shall be accompanied by a pleading setting forth the claim or defense for which intervention is sought. The same procedure shall be followed when a statute gives a right to intervene.
Del. Fam. Ct. R. Civ. P. 24