Pennsylvania Births, Dauphin County 1757-1825
John T. Humphrey

He doesn't list baptismal sponsors. I would try and find the church records for these churches and see if you could match up baptismal sponsors. You may also want to find the burial records too.

All churches in the Harrisburg area or Dauphin County showing Martin baptismal records;

Surname - Martin
ZION LUTHERAN, Harrisburg Baptisms
Cornelius Ackinson, 16 Jun 1799 Parents James & Kisia
Jane, 4 Jun 1797 parents James & Kissia
John, 21 apr 1795 Parents James & Kissia

Georg Stein, 20 Oct 1811 Parents MARTIN & Paille

Johannes, 13 Mar 1800 Parents John & Eva

Luther, 2 Oct 1817 John & Mary

Mary, 9 Dec 1821 Parents John & wife
Henrietta, 25 Apr 1816 Parents John & wife

Elisabet, 29 Nov 1813 Parents John & Sophia
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SALEM REFORMED, Harrisburg Baptisms
Maria Margaret, ? 1818 Parents Peter & Catharina
Elisabeth, 25 Jul 1816 Parents Peter & Catharina

FANNY Catharine, 11 Feb 1819 Parents William & Catharine

Johann Georg, 21 Nov 1790 Parents Christoph & Margaretha

Anna Sabina, 23 Sep 1788 Parents Nicholas & Maria Regina
Johann Daniel, 31 Jan 1794 Parents Nicol & Maria Regina
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SHOOP'S CHURCH, Lower Paxton Twp. Baptisms
David, 14 Mar 1781 Parents not given

Johannes, 10 Jul 1784 Parents Johannes & Regina
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HUMMELSTOWN LUTHERAN, Derry Twp., Baptismal Records
DANIEL, 20 Mar 1811 Parents MARTIN & Elisabeth
EUPHRONICA, 4 Feb 1805 Parents MARTIN & Elisabeth Nufes
(NOT MARRIED YET)

John Wolfgang, 4 Oct 1806 Parents John & wife
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HILL or MAXEE LUTHERAN, Derry Twp. Baptismal Records
CHRISTIAN, 8 Aug 1813 Parents Martin & Eliabeth

Sarah, 10 Mar 1820 Parents Daniel & Elisabeth
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MIDDLETOWN LUTHERAN, Middletown Twp. Baptismal Records
Elisabeth, 27 Mar 1808 Parents Jacob & Catharina