Growing up south of Boston, it often seemed to Kathy Gillcrist that her personality never quite matched up with her adoptive family. While her parents had been shy and quiet, she was “a bossy little girl with a vivid imagination” and a Type A personality, she wrote.

When she took a DNA test decades later and eventually unearthed the identity of her birth father, it came as no surprise to find a man who exhibited the same kind of drive and flair for the dramatic.

But Gillcrist, 63, says she could not have anticipated just how notorious he would be: Her birth father, William Bradford Bishop Jr., is accused of murdering his wife, mother and three sons with a small sledgehammer, she would learn. The notorious fugitive from Bethesda has been wanted by the FBI since 1976, at one point appearing on the agency’s Ten Most Wanted list.

When Gillcrist first found out about his identity, “I just laughed,” she told WECT last week. “We have a great sense of humor in my adoptive family and I thought, ‘Of course, my father’s a murderer!' ”

That revelation, which she also recounted in a new book, “It’s in my Genes,” is the latest case of a DNA test — a cheek swab or vial of saliva meant to learn more about family ancestry — leading to a very different kind of genealogical discovery, sometimes with troubling consequences.

About three years ago, an Oregon doctor and former sperm donor learned on Ancestry.com that he had unknowingly fathered at least 19 children, all of whom lived a short drive away from his own family. Two childhood best friends in Maryland recently unearthed the fact that they share a father. Others have learned their family doctor was actually their biological parent, or that their dad had a second secret family.

Yet even as genealogical databases become increasingly popular, few can claim to have found ties to a fugitive believed to still be on the loose. In 2016, the FBI said a team of federal and local law enforcement officers had spent the past two years following up on more than 650 leads to locate Bishop.

When she first conducted a 23andMe DNA test around the same time, Gillcrist told WECT, she only received one distant family connection from the vial of spit she had sent in: Susan Gillmor, a third cousin living in Maine.

Besides their similar last names, the two women discovered a number of uncanny parallels: They both majored in English in college, both went on to become teachers, and both had the same blonde hair.

But Gillmor, herself a genealogist, offered to dig a bit deeper for Gillcrist’s birthparents. When she finally landed upon Bishop after a years-long search, she decided to only give her third cousin his name.

“Is it someone famous?” Gillcrist remembered asking.

She needed no convincing that Bishop was in fact her father. His children — her siblings — resembled her more than her own kids, she recalled. “And when I look at the behaviors and characteristics, it’s more than clear in my mind,” she told WECT, noting they both had struggled with insomnia.

As The Washington Post’s Dan Morse reported in 2014, Bishop was a skilled world traveler and amateur pilot who worked for the State Department Foreign Service, with postings in Italy and Botswana.

He had Gillcrist with her birth mother in 1957 but married his high school sweetheart two years later, eventually settling in Bethesda with her, his mother and three sons.

In 1976, he was passed over for a promotion and apparently took it out on his family, police said, bludgeoning all five to death in their sleep. After the attacks, he drove nearly 300 miles to a swampy corner of North Carolina, dug a shallow grave and lit their bodies on fire.

Authorities would find his car several hours away, at Great Smoky Mountains National Park, with maps and hiking information inside. But Bishop himself had disappeared.

Nearly three decades later, in 2014, the FBI placed him on its Ten Most Wanted Fugitives list, making it clear the agency believed he was still alive. Officials said that with fluency in five languages, he could have easily created a new life for himself somewhere abroad. He would be 84 years old today.

Gillcrist, who was in her late teens at the time of the murders, said her birth mother had listed a different name for her father on adoption records and on her original birth certificate.

“Either she was really confused or was leading a life that involved keeping a lot of secrets,” she told Bethesda Beat. “There is a lot of mystery.”