http://www.divorcenet.com/states/pennsylvania/pennsylvania_child_support_paternity some information is from this website. Also I read the statutes below.
20 Pa.C.S. § 2107 (2007)
§ 2107. Persons born out of wedlock
(a) CHILD OF MOTHER. --For purposes of descent by, from and through a person born out of wedlock, he shall be considered the child of his mother.
(b) Deleted by 1978, Nov. 26, P.L. 1269, No. 303, § 1, imd. effective.
(c) CHILD OF FATHER. --For purposes of descent by, from and through a person born out of wedlock, he shall be considered the child of his father when the identity of the father has been determined in any one of the following ways:
(1) If the parents of a child born our of wedlock shall have married
each other.
(2) If during the lifetime of the child, the father openly holds out
the child to be his and receives the child into his home, or openly
holds the child out to be his and provides support for the child which
shall be determined by clear and convincing evidence.
(3) If there is clear and convincing evidence that the man was the
father of the child, which may include a prior court determination of
paternity.
23 Pa.C.S. § 4343 (2007)
§ 4343. Paternity
(a) DETERMINATION.-- Where the paternity of a child born out of wedlock is disputed, the determination of paternity shall be made by the court in a civil action without a jury. A putative father may not be prohibited from initiating a civil action to establish paternity. The burden of proof shall be by a preponderance of the evidence. Bills for pregnancy, childbirth, postnatal care related to the pregnancy and genetic testing are admissible as evidence without requiring third-party foundation testimony and shall constitute prima facie evidence of amounts incurred for such services or for testing on behalf of the child. If there is clear and convincing evidence of paternity on the basis of genetic tests or other evidence, the court shall upon motion of a party issue a temporary order of support pending the judicial resolution of a dispute regarding paternity. The Supreme Court shall provide by general rule for entry of a default order establishing paternity upon a showing of service of process on the defendant and a subsequent failure to appear for scheduled genetic testing.
(b) LIMITATION OF ACTIONS.--
(1) An action or proceeding under this chapter to establish the
paternity of a child born out of wedlock must be commenced within 18
years of the date of birth of the child.
(2) As of August 16, 1984, the requirement of paragraph (b)(1) shall
also apply to any child for whom paternity has not yet been established
and any child for whom a paternity action was brought but dismissed
because of a prior statute of limitations of less than 18 years.
(c) GENETIC TESTS.--
(1) Upon the request of any party to an action to establish paternity,
supported by a sworn statement from the party, the court or domestic
relations section shall require the child and the parties to submit to
genetic tests. The domestic relations section shall obtain an
additional genetic test upon the request and advance payment by any
party who contests the initial test.
(2) Genetic test results indicating a 99% or greater probability that
the alleged father is the father of the child shall create a
presumption of paternity which may be rebutted only by clear and
convincing evidence that the results of the genetic tests are not
reliable in that particular case.
(3) To ensure the integrity of the specimen and that the proper chain
of custody has been maintained, the genetic tests of the biological
mother, the child or children in question and the alleged father should
be conducted by an established genetic-testing laboratory in the course
of its regularly conducted business activity, and certified records
should be issued. The certified records shall be admissible into
evidence without further foundation, authentication or proof of
accuracy if no objection is made within ten days prior to trial. The
laboratory must be certified by either the American Association of
Blood Banks or the American Association for Histocompatibility and
Immunogenetics.
(4) If the court or domestic relations section orders genetic testing,
the domestic relations section shall pay the cost of the test, subject
to recoupment from the alleged father if paternity is established.
(5) A determination of paternity made by another state, whether through
judicial proceedings, administrative proceedings or by acknowledgment
of paternity, shall be given full faith and credit in the courts of
this Commonwealth.
(6) A determination of nonpaternity made by another state with respect
to a public assistance recipient shall not be binding upon the
Department of Public Welfare unless the defendant shows that the
department had actual notice of the proceedings, including the date and
time of any trial, and a fair opportunity to participate in all
material proceedings through counsel of its own choice.