Sam Phillips wanted to know if he was Jewish.

Karen Cox-Dennis wanted clues as to why she was diagnosed with diabetes at the age of 48.

Jeff Haan, who was adopted, wanted to know his ethnic makeup.

And Dave Austin wanted to know why the heck someone came to his stepmother’s door, claiming to be his long-lost half-brother.

Four strangers took mail-in DNA test kits for different reasons.

All of them found out something unexpected: They are related.

DNA tests are rising in popularity, even as concerns about privacy and accuracy trouble users. AncestryDNA, perhaps the most ubiquitous brand, sold 1.5 million kits last holiday season, tripling its sales from a year ago. It now has more than 7 million users in its database. 23andMe stocks its kits in the pharmacy aisles of Target and Walgreens, making a purchase as easy as buying Band-Aids.

With so many people sending away their DNA, there are bound to be consequences. Almost as soon as these saliva-collecting kits arrived in mailboxes, stories started popping up in the news media and social media. Stories of families being brought together — or torn apart — by revelations of infidelity, adoption or even switches at birth. Stories of people whose need to know the truth outweighed the risks of exposing the mysteries in their genetic code.

This is one of those stories.

We tracked how four people who had never met each other found out via their DNA that they were family.

Sam: Mistaken heredity

For Sam Phillips, the decision to test his DNA was simple.

“I wanted to know what I was,” said the jovial 77-year-old with a hearty laugh.

When Sam was a child, his father had worked for a Jewish man at a clothing store in Wadena, Minn., and people had often thought Sam and his brother were Jewish. Even when he got older, people assumed Sam was Jewish: A Jewish girl in college “chased me around for a while,” said Sam. And his brother almost lost a job at a drugstore in Bemidji because of anti-Semitism.

The family had a neighbor who was adopted as a Jewish refugee from Europe. Sam’s father helped the neighbor track down his family history, and learned that the neighbor’s original surname, coincidentally, was also Phillips. That convinced Sam that he was Jewish, too.

After a lifetime of not knowing for sure, he finally took the AncestryDNA test in October 2015.

The Battle Lake., Minn., man didn’t get the result he’d expected. He wasn’t Jewish at all.

But by taking the test, he helped solve mysteries in the lives of three complete strangers.

Jeff: Sucked into the search

Jeff Haan had never wanted for a loving family.

The bespectacled 54-year-old from East Greenwich, R.I., had one in his adoptive parents, both of whom died years earlier. But for Christmas 2015, his mother-in-law, meaning well, gave him a DNA kit from 23andMe.

“Because I had no history, she thought it would be interesting for me to see if I’m mostly Scandinavian or Eastern European,” Jeff said. “She just didn’t think that far ahead.”

Jeff didn’t, either.

He’d had no idea that by taking the simple test, he would get sucked into a search for his biological parents. The results showing where his ancestors came from were “fascinating,” he said. But he became even more interested in a list of people the site suggested as possible relations. One of them was Karen Cox-Dennis.

Karen: Driven by concern

For decades, a family mystery had dogged Karen Cox-Dennis, a candid 51-year-old producer of commercials from Tallahassee, Fla. But she had long hesitated in trying to solve it.

On her deathbed, Karen’s mother admitted to her husband that she’d had an affair and their daughter was not his.

Karen had suspected the truth, but didn’t know for certain until after her father died. Then, she had strands of his hair DNA-tested and learned that she and the man she had known as her father were unrelated.

It wasn’t until many years later, when she was diagnosed with late-onset Type 1 diabetes, that she wanted to learn more about her history. So she took a 23andMe test.

In April 2016, Karen and Jeff were identified on the site as possible relatives. Jeff messaged Karen through the 23andMe site. At first, she was taken aback.

“I said, ‘Listen, I don’t speak this language, I don’t have time for this, I’m sorry.’ But Jeff did the investigating and ran with it.”

Eventually, she came around, and the two teamed up together to find their families. They both tried using other genetic testing companies, but none of the results gave them any clues about who their biological parents were or how they were related to each other.

Then, Jeff sent his saliva sample to Ancestry. That’s where he came across Sam, whose DNA identified him as a first cousin once removed.

Since learning he wasn’t Jewish, Sam had immersed himself in his family history, tracing his ancestors back several generations, from North Dakota and Wisconsin to Norway and Wales.

Jeff contacted Sam through the Ancestry website, asking if Sam could help him find biological relatives.

Sam thought through his family tree. Jeff had grown up in Michigan, and one of Sam’s now-deceased first cousins had lived in Michigan. Sam gave Jeff the name of that cousin.

Jeff tracked down the man’s widow and went to see her.

Dave: Guilt and Thanksgiving

Dave Austin, a quippy 59-year-old from Lowell, Mich., got a strange call one day in October 2016.

“A guy stopped by today from Rhode Island,” said his stepmother, “and he thinks that he might be your dad’s son.”

“I said, ‘OK. Really?’ ”

His stepmother then told Dave something she had learned years before: His father had another child from a previous relationship.

The revelation, Dave said, was “awkward.” He didn’t know how he could help this stranger who had shown up looking for his relatives. And he felt guilty.

“I felt bad on behalf of my dad, that he would have done something like that,” Dave said.

Some family members wondered if it was a scam. But it wasn’t completely implausible that this stranger was related to him. Dave’s father and mother had divorced when Dave was 4, and his father was between marriages when Jeff would have been conceived. The two men grew up in the same part of Michigan. They both became engineers, and both shared a passion for cycling.

Dave offered to take a DNA test, and it was a “super-high match,” he said. He and Jeff were half-brothers.

“I see our biological father in his face,” Dave said of Jeff.

Jeff went home to Michigan that Thanksgiving, and invited Dave to join him and his adoptive family.

“That was really heartwarming,” Dave said. “It was just very cool, to not even know someone, and he invited us into his other family.”

Reward vs. risk

Reunions like these are happening all the time, said Jennifer Utley, a family historian at Ancestry.

“With over 10 million family connections made every day, you may discover a part of your family history story you never knew — one of those cousins might have a photo of your great-grandmother that you’ve never seen before.”

But the process is not without risk, especially since it can divulge information that can affect entire families.

University of Minnesota genetic counselor Heather Zierhut has been tracking the rise of “recreational genomics” as an assistant professor in the College of Biological Sciences.

“A lot of people do this test thinking they’re going to learn something about themselves, and then realize, wow, this impacts an entire family or community,” said Zierhut.

Some people who are searching for a relative have their hopes crushed when they can’t find that person. Some learn of serious health information they may not be able to interpret — and that may or may not be a predictor of their own health. Others find a relative who, for whatever reason, didn’t want to be found.

There are “stories of people going into these parts of their lives they thought had been closed and now have been opened up,” Zierhut said.

A piece of the puzzle

With the paternal half of Jeff’s mystery solved, thanks to Sam, Jeff suggested that Karen try Ancestry, as well. Sure enough, she, too, matched with Sam as a first cousin once removed.

Karen told Sam that she was born in California, and Sam suggested another of his first cousins as her potential biological father. The man Sam referred her to was, Karen said, a “riverboat gambler and ladies man” who had spent time in California. In late 2016, he was on his deathbed in Oregon.

Karen flew to see him. She showed the man a picture of her mother and “he remembers everything,” Karen said. “He says, ‘Yes, we had an affair at a motor court every Friday night for six months. You’re mine and I love you.’ In one breath.”

Karen asked him if he would provide a saliva sample and he agreed. It was a match. From there, she tracked down three additional half-siblings, plus uncles and cousins.

“It was a great gift, what Sam and Jeff have given me,” she said. “The last piece of my genetic puzzle. I can sleep at night.”

Connecting the dots

During the year or so it took for Jeff, Karen and Dave to find each other — through the DNA sites, social media, in person — Sam watched on in amazement.

“I was the middleman in this deal,” he said. “It’s been just an incredible experience. It’s like I’m sitting here watching a story on television and I’m part of it.”

Jeff considers Sam, who is one generation older than the others, “the patriarch of this group.”

Sam had been asking his newfound family to visit him for a while. One weekend in March, they met face-to-face in a Minneapolis hotel.

They had dinner and brunch together, watched the St. Patrick’s Day parade as it marched through downtown Minneapolis, and celebrated Jeff’s 54th birthday.

Sam brought along poster boards he made of family pictures and timelines that explained the group’s connections, a genealogy art project writ large.

Even though they were gathering for the first time, “it seems very comfortable and familiar,” Karen said.

After all, they’d had a relationship with each other for a while. Albeit an unusual one, uncovered bit by bit.

“We all had these incomplete packets of information, but none of us lost interest,” Jeff said. “We kept up these phone calls and e-mails with complete strangers and over the course of almost a year, we solved this riddle.”

The four of them still wonder about the serendipitous way they found one another, at how they “connected the dots.”

While they were all seeking something else, they found an accidental family.