How I helped solve a century-old Presidential paternity question using genetics

Since his birth in 1878, Philippine Commonwealth President Sergio Osmeña’s father has never been definitively identified, although two men were alleged to have been either his father, Pedro Gotiaoco and Antonio Sanson. The quest to discover the identity of Osmeña’s paternity has been 145 years in the making. While he lived, he refused to talk about his parentage. It’s unclear if he spoke about his father to his children and grandchildren, but there are stories that he did, yet living descendants today are unanimous in saying they are unaware of his true father’s identity. Most likely, he brought the secret identity of his father to his grave. For years since his death in 1961, his family has been trying, unsuccessfully, to find records or documents to show his father’s identity. It was only recently when the family decided to explore using DNA testing to answer their questions as all archival documents and other traditional genealogical avenues have already been exhausted.

Photo of former Philippine president Sergio Osmeña

National Library of the Philippines (distributed by Philippine Presidential Museum and Library) – http://www.malacanang.gov.ph

As one of the few professional genealogists in the Philippines and one of the even fewer genealogists who have wholeheartedly embraced genetic genealogy as an integral and important tool to help further expand family history research, I was approached and hired by descendants of President Osmeña to help them finally answer the question of who their ancestor’s father was. After analyzing the family trees involved in the project: the Osmeña family tree and both genealogies of the men suspected of being his father, I ordered a Y-chromosome test to be utilized to determine Osmeña’s paternity. I was fortunate enough that the three lines to be tested all had male lineal descendants since the test was a male-specific genealogical DNA test used for exploring a man’s patrilineal or direct father’s ancestry.  My goal was simple; if we could compare the Y-DNA of a direct male-line descendant of President Osmeña with the Y-DNA of direct male-line descendants of both the Gotiaoco and Sanson families, then we would finally have scientific and definitive proof of who Don Sergio’s father was. A month after the samples were received by the DNA testing company, definitive results were received: a comparison of the 23 markers of the Osmeña DNA with Gotiaoco’s did not match in many markers, while a comparison with Sanson’s clearly indicated a 100% match in all markers. Thus, according to the analysis of the DNA laboratory and with the help of traditional genealogical tools, Sergio’s descendants and the Sansons cannot be excluded from being of the same male lineage and Sergio Osmeña’s descendants have a 99.982% chance of being patrilineally related to the Sansons. The 100% match of the 23 markers also clearly indicates that the Osmeñas and Sansons are closely related in the patriline and share a more recent common ancestor (MRCA) within 3-5 generations. Thus, the answer to the 145-year question of a former Philippine president’s paternity was finally answered and solved.

This discovery has only been possible because of advancements in modern science. DNA testing has allowed many families to prove and disprove family lore, and I have continued to recommend genetic genealogy to many of my clients. Combining traditional genealogical tools with modern DNA testing, I have been able to discover the father of a former president. This has truly been an amazing journey, the search for and discovery of President Sergio Osmeña’s father, a once-in-a-lifetime opportunity to contribute to the collective story of our nation.