By Anne Levin

Growing up on Long Island with his mother and stepfather, Matt Katz had little contact with his biological father — or the man assumed to be his dad.

It was later in life, when his future wife took him to meet her grandmother, that he started to wonder. The grandmother commented that Katz, who like his fiancé was raised Jewish, actually looked Irish. Katz was, by then, a well-known journalist. His curiosity was piqued.

He decided to take a home DNA test. The results were shocking. He was half Jewish, and half Irish. Since his mother’s first husband, the man thought to be his father, was Jewish, it didn’t make sense.

As documented on Katz’s award-winning podcast, “Inconceivable Truth,” the revelation was the beginning of a search for his birth father that would take Katz across the Atlantic and into the ethically dubious world of 1970s infertility treatments. Along the way, he would meet half-siblings and family members he never knew existed.

Katz will talk about that search at a program being held on Wednesday, January 8 at 6:30 p.m. at Princeton Public Library. Joining Katz will be his friend and fellow journalist, Princeton resident Charles Stile.

“We’re so pleased to be hosting longtime friends Matt Katz and Charlie Stile discussing Matt’s remarkable podcast,” said Tim Quinn, the library’s director of marketing and communications, who will introduce the speakers. “We hope the community will take time to listen to ‘Inconceivable Truth’ before coming to the program. It is a thought-provoking story that should inspire a fascinating conversation.”

Katz is an investigative reporter who covered Chris Christie, first for the Philadelphia Inquirer and then WNYC radio, winning a Peabody Award for a series about the Bridgegate scandal. He recently became the executive producer of “City Cast Philly,” a daily news and culture podcast and newsletter about Philadelphia. Stile, an award-winning veteran political columnist at The Bergen Record/USA Today Network, will talk with Katz not only about his personal journey, but also about the ramifications of the unregulated infertility treatments of the 1970s.

“There’s a whole generation out there that until ancestry.com came along, wouldn’t know that family members even existed,” said Stile, who was relistening to Katz’s podcasts in preparation for the program. “I think it’s fascinating that he’s helping to redefine what a family is.”

As part of his investigations, Katz was able to track down and interview the doctor who had helped his mother conceive by using donated sperm. Used to asking tough questions to track down a story, Katz was a little uncomfortable about asking his mother about her fertility treatments. But he persisted.

It turned out that she thought the doctor had used her then-husband’s sperm. That didn’t jibe with what the doctor said to Katz — that he always told his patients he was using donated sperm, which was usually donated by medical students looking to make some extra money.

Katz has talked about his journey at New York University’s audio journalism program, and at the Pen and Pencil Club in Philadelphia. He was also profiled on a Father’s Day segment of the television show CBS Sunday Morning.

“I haven’t spoken specifically to a more general audience, but I have gotten over 1,000 messages from listeners over the past six or eight months,” he said.

The three siblings Katz has met through his search are a big part of his life today. “One of them recently moved to the Philadelphia area, where we live, and we hung out with our kids. The cousins got to be together,” he said. “And our kids kind of look alike. They have similar coloring.”

While he has come to realize there was a lot of unregulated, sometimes unsavory activity in the early days of the infertility industry, “I’m both grateful to have life and exist,” Katz said. “But what was done in those decades, when it came to the information and the lack of transparency, and sometimes the outright manipulation by doctors, was unethical in the least.”

Stile is impressed by his friend’s bravery and persistence. “A lot of people may have curiosity about their origins, and might dig a little bit, but Matt was relentless,” Stile said. “And having to confront difficult questions about his mother and adoptive father is not an easy task. I think it really shows the skills and talents of a great investigative reporter who is not thwarted by a dead end.”

To find out if Katz ultimately identifies his real father, stream “Inconceivable Truth” on Apple Podcasts, Spotify, or Amazon Music. For more information about the January 8 program, visit princetonlibrary.org.