ST. LOUIS » Growing up, Khrys Vaughan always knew that she had inherited her looks and mannerisms from her father, and that her appreciation for tradition and old-fashioned gentility stemmed from her parents’ Southern roots. But those facets of her self-image crumbled when she was told, at age 42, that she had been adopted.

She began searching for her origins, only to find out that her adoption records had been sealed, a common practice in the 1960s. Then Vaughan stumbled across an ad from a DNA testing company offering to help people who had been adopted find clues to their ancestry and connections to blood relatives.

About five weeks after shipping off two tiny vials of her cells from a swab of her cheek, Vaughan received an email informing her that her bloodlines extended to France, Romania and West Africa. She was also given the names and email addresses of a dozen distant cousins. This month, she drove 208 miles from her hometown here to Evansville, Ind., to meet her third cousin, the first relative to respond to her emails. Vaughan is black and her cousin is white, and they have yet to find their common ancestor. But Vaughan says that doesn’t matter.

"Somebody is related to me in this world," she said. "Somebody out there has my blood. I can look at her and say, ‘This is my family."’

A growing number of adoptees, now in the thousands, are turning to DNA testing companies in hopes of piecing together the puzzles of their beginnings. Some long to learn whether their family trees first bloomed in Ireland or Italy, Europe or South America. Others want to know whether they are genetically predisposed to developing diabetes, cancer or other diseases. Most adoptees are hungry for information that will lead to their birth parents, but some are also expanding their conception of family as they embrace a far-flung constellation of second, third and fourth cousins.

DNA testing companies are stepping up their efforts to reach this community, posting advertisements on adoption message boards and testimonials on their websites. Adoptees and some groups that serve them are also spreading the word.

"There has never been a better time to establish your biological identity," says the website of Adoption.com, which promotes its efforts to unite adoptees and blood relatives online.

Genetic testing has surged in popularity over the past decade as the cost of analyzing cell samples has dropped and as Americans have grown more interested in learning about their heritage. As a result, some companies have amassed enough DNA samples that they can offer to help adoptees identify their kin, bringing hope to people born in an era when adoption records were routinely sealed, leaving few paper trails to follow.

Several companies provide tests that can confirm whether adoptees are related to individuals they already know. Others cast a wider net by plugging DNA results into databases that contain tens of thousands of genetic samples, provided mostly by people searching for their ancestral roots. The tests detect genetic markers that reveal whether people share a common ancestor or relative.

Some experts on adoption and genetics have criticized ancestry and genealogy testing companies, saying they are, at times, connecting people whose genetic links are tenuous — in effect, stretching the definition of a relative. Nevertheless, the growing popularity of the tests, combined with social media sites that connect people day to day, has given some adoptees a sense of family that feels tangible, intimate and immediate.

Within minutes of receiving the names of her distant relatives, Vaughan, a freelance project manager, was admiring their photographs on Facebook. Another adoptee who found family through DNA testing, Kathy Borgmann, a 49-year-old corn farmer in New Palestine, Ind., exchanged emails with cousins who delighted her by saying, "Welcome to the family."

Alan Bogner of Olympia, Wash., felt such kinship with his newly discovered second and third cousins that he attended their family reunion in Iowa. He learned, among other things, that many of them were also tall — he is 6-foot-5 — and that they shared his liberal politics.

"It sounds so baloney, but they’re just so much like me," said Bogner, 54, who works for the governor’s office.

The tests have their limitations. The price of testing can range from $99 to more than $500, putting them out of reach for some people. Company officials also caution that it is much more common to find second and third cousins than birth parents or siblings.

Neil Schwartzman of Montreal struck gold when his test connected him with his sister — "I was gob-smacked," he recalled — but such cases are not typical.

Company officials say the odds are improving, though, as more people pay for tests and add their DNA to the pool of potential matches. Two testing companies — Family Tree DNA and 23andMe — have databases that contain samples from 350,000 and 125,000 people, respectively, and their executives say those numbers are rising. In recent years, about 9,000 of their customers have identified themselves as adoptees, company officials say, but they believe the actual number is larger since not everyone shares their reasons for testing.

For somebody looking for a match, "maybe there’s no one in the database today, but in two years a first cousin might be there," said Anne Wojcicki, the chief executive of 23andMe.

DNA testing companies, which compete for customers, do not pool their databases, so people often submit samples to more than one.

Not everyone is hoping to find new relatives. Some adoptees who have found genetic matches have been rebuffed by their distant kin. Most people take genealogical DNA tests to fill gaps in their family trees, not to find new members of their clans. Bogner said several cousins identified through DNA testing stopped communicating once they learned he was adopted.

"It was horribly disappointing," he said.

Elizabeth Bartholet, an expert on adoption at Harvard Law School, said the proliferation of testing highlights the need for broader access to adoption records. In the meantime, she says, adoptees would be better served by nurturing the relationships they already have.

But Vaughan, who is now 44, said her newfound relatives have filled a void in her life. Her adoptive father died when she was 9 and she had found comfort over the years knowing that she shared his smile.

"I was crying because I wasn’t Daddy’s little girl," said Vaughan, describing the day that her adoptive mother finally told her the truth. "I needed to find my place in the world."

She sent out her first email to a cousin identified by Family Tree DNA in March. It landed in the inbox of Jennifer Grigsby, a research analyst from Somerset, Ky., who read it with astonishment. Grigsby had taken a DNA test to learn more about her lineage.

"I wasn’t looking for a new relationship," she said. But when the two women started talking, "there was like an instant connection," said Grigsby, 37.

They started exchanging emails and Facebook messages every week, and calling once or twice a month. A few weeks ago, they decided to meet in Evansville, midway between their homes. But three days before their get-together, Vaughan learned the identity of her birth mother. The courts had determined that her mother had died in 2005, which meant that her name could finally be released. The discovery led her to four sisters.

Grigsby offered to cancel their plans so Vaughan could connect with her siblings. But Vaughan would have nothing of it. Last week, she drove more than three hours to see the first blood relative who had embraced her as family.

"Finally!" she said when they met, and she hugged her third cousin like she would never let go.

© 2012 The New York Times Company