John Stapleton, 55, knew since he was a kid that he was adopted. But it wasn’t till the late ’90s that a darker truth was revealed to him in a newspaper article.

The Akron, Ohio, native and his adopted sister Cindy were black-market babies, acquired through an elaborate baby-selling operation run by a Georgia physician.

“My father burst into tears when he found out,” Stapleton tells The Post. “He knew he adopted us. But he didn’t know about the black market.”

John and Cindy were just two of more than 200 newborns sold by Dr. Thomas Hicks, a doctor in McCaysville, Ga., who was selling babies out of the back door of his clinic in the 1950s and ’60s. Most of the children were adopted by Akron-area families who couldn’t afford the costly traditional route of adoption — and many of whom were unaware of Hicks’ dark methods.

The mind-blowing story is the subject of a new three-part TLC series (premiering Oct. 9), “Taken at Birth,” which attempts to crack open the mystery of the doctor’s scheme and reunite some of the “Hicks babies” with their birth families.

But in untangling the complicated web surrounding Hicks, the show opens a small town’s vault of secrets, leading to bittersweet reunions and DNA bombshells.

At the center of the show is Jane Blasio, a Hicks baby determined to learn the truth about the late physician and her own origins. She travels to McCaysville and enlists TLC’s “Long Lost Family” hosts Chris Jacobs and Lisa Joyner to help investigate.

“[Jane] has been fighting for me and for all of us for years,” says Stapleton, who retired from the Army a few years ago. “And she has never given up.”

John Stapleton Taken at Birth
John Stapleton and his sister Cindy were both sold on a black market as babies.John Stapleton

In Stapleton’s case, his biological roots are just starting to poke through the surface. After submitting his DNA to Ancestry.com last year, he has found key family members — though not all of them were keen on a warm, fuzzy reunion.

Stapleton, who now lives in Long Beach, Calif., with his longtime girlfriend, was reunited with a half sister, with whom he shares a father. And the pair have formed an easy bond: “We have matching DNA tree tattoos on our backs,” Stapleton says of his sister Atress Davis.

Through town records, he and Atress, who is not a Hicks baby and was raised by her maternal family, found their father, who is now 83. He has no interest in connecting with his two long-lost children.

“We tried to contact him during the filming. He was in denial,” says Stapleton.

John Stapleton and his biological sister Atress Davis.
John Stapleton and his biological half sister Atress DavisJohn Stapleton

But he has found solace in the large network of Hicks babies who share resources, dejection and hope.

“Once you sit down and start meeting people individually and you start listening to everybody’s story, it’s like a big family,” adds Stapleton.

As for Hicks, Stapleton knows the story isn’t cut and dried.

“I know abortion was illegal at the time, and then I think he was running into people who couldn’t afford adoptions,” he says. “I think, at first, it was under the table, and then he had seen there was money involved. It turned into a business. [But] I don’t think it initially started that way.”

He knows he lucked out by landing with his loving parents, the late Jean and Robert Stapleton.

“Honestly, I am grateful for the life I have had. I would be afraid to change anything.”

But still, deep down, Stapleton has a desire to learn more about his birth family.

“I would like to find more answers. The hardest thing is, emotionally, I don’t show a lot. But on the inside, it’s a totally different story. I am only human.”