(a) Intervention of right. On timely motion, a person shall be permitted to intervene as a party in a probate proceeding: (1) When a statute confers an unconditional right to intervene; or (2) The moving party is an interested party under Rule 17 but did not receive personal notice of the proceeding. (b) Permissive intervention. On timely motion, a person may be permitted to intervene in a probate proceeding: (1) When a statute confers a conditional right to intervene; (2) When the moving party has a legal interest, the protection of which involves a question of law or fact in common with the probate proceeding; or (3) When a party to the proceeding relies upon any statute or executive order administered by a federal or state governmental office or agency or upon any regulation, order, requirement or agreement issued or made pursuant to the statute or executive order, the office or agency may be permitted to intervene in the proceeding. In exercising its discretion, the court shall consider whether the intervention will unduly delay the proceeding or prejudice the interests 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.