(a) An alleged father, as that term is defined in Section 103 of this Act, must commence an action to establish a parent-child relationship for a child having a presumed parent not later than 2 years after the petitioner knew or should have known of the relevant facts. The time the petitioner is under legal disability or duress or the ground for relief is fraudulently concealed shall be excluded in computing the period of 2 years.
     (b) A proceeding seeking to declare the non-existence of the parent-child relationship between a child and the child’s presumed father may be maintained at any time by a person described in paragraphs (1) through (4) of subsection (a) of Section 204 of this Act if the court determines that the presumed father and the mother of the child neither cohabited nor engaged in sexual intercourse with each other during the probable time of conception.
     (c) An adjudication under this Section shall serve as a rebuttal or confirmation of a presumed parent as defined in subsection (p) of Section 103.