(a) If a child has an acknowledged parent, a signatory to the acknowledgment described in Section 301 of this Act or related denial may commence a proceeding seeking to challenge the acknowledgment or denial or challenge the paternity of the child only within the time allowed under Section 309 of this Act.
     (b) If a child has an acknowledged parent or an adjudicated parent, an individual, other than the child, who is neither a signatory to the acknowledgment nor a party to the adjudication and who seeks an adjudication of parentage of the child must commence a proceeding not later than 2 years after the effective date of the acknowledgment or adjudication.
     (c) A proceeding under this Section is subject to the application of the principles of estoppel established in Section 610 of this Act.