First came the home DNA kits. Now come the support groups

23 and Me is one of the companies offering home DNA tests. (Nathan Siemers/Creative Commons)Credit: Nathan Siemers/Creative Commons

The home DNA kit from AncestryDNA was a gift, and it was supposed to be nice. But when Catherine St Clair sent in her sample, she instead learned a shocking truth about herself: She was not the biological child of the man she knew her entire life as “Daddy.’’

The trauma sent her to his Texas gravesite, where she lay down and sobbed. “I felt I lost him all over again,” she said.

First came the home DNA kits, with their promise of light fun. Learn if your family is part Scottish! Go on a DNA-inspired globe-trotting trip! Connect with distant cousins!

Now comes the fallout: As millions upload genetic results to AncestryDNA and 23andMe and smaller firms, many are learning devastating news. They’re not their sister’s full sibling, not related by blood to anyone in their entire family, not who they thought they were.

“I feel like I’m a freak now,” said St Clair, of Texas, who was 55 in 2017 when her world changed.

More than 26 million people have taken an at-home DNA test, according to an estimate by the MIT Technology Review. The emotional pain and confusion set off by such inadvertent discoveries of family skeletons has become so widespread that support groups are proliferating online, and one, run by St Clair, is nearing 5,000 members.

So many people are dealing with variations on DNA surprises that there’s a hunger for even very narrow, splinter support groups.

“Somebody who found out they were donor conceived wanted to be in a support group only with other people who had made that same discovery,” said Brianne Kirkpatrick , a Virginia-based genetic counselor and DNA consultant.

She already runs several support groups, including one for wives whose husbands have just learned they have an adult child, conceived before the marriage, perhaps during a one-night stand.

AncestryDNA and 23andMe ’s ancestry kit retail for $99 and have become the on-trend present for weddings, birthdays, and more. But they can become gift-wrapped bombshells. Merry Christmas, next year at this time we won’t be speaking!

Both companies warn consumers about discovering what AncestryDNA calls “unanticipated facts about yourself or your family.’’

There are many happy DNA stories, of course, but the people turning to support groups aren’t there because they’re delighted to have found their biological father. They thought they already knew him. The pain is raw.

“My anger towards my mother subsided for a bit today,” one member of St Clair’s Facebook group wrote earlier this month.

“I spoke with her briefly today after icing her out since I found out the truth about my dad. She talked about how ashamed she feels, and how sorry she is. I’m mad at her, yes, but my heart breaks for her.”

“No other words can describe my feelings other than pure betrayal,” another member wrote. “My mother pretends she never knew I wasn’t my father’s . . . I feel alone. . . . Sad for my father who was betrayed.”

St Clair shared the posts after receiving authorization from the authors. She said that members come after learning they are not biologically related to at least one of their parents.

That’s a situation that can happen for many reasons, she e-mailed the Globe, “most commonly the result of affairs, donor-conception (this covers both egg and sperm donors), late-discovery adoptions, and disturbingly commonly — sexual assault. . . . There are also instances of switched-at-birth, black-market (illegal) adoptions, and — sadly — incest (a cousin, sibling or parent).”

A member of another private online group, run by Kirkpatrick, wrote that she feels the family history she so lovingly compiled now feels like a lie after she learned her father had another child, giving her a half sister she never knew about.

“I felt like my whole family died on the same day,” Michelle wrote on a blog for Kirkpatrick’s website. “Family is more than biology and I’ve always known that, but everything has changed for me.”

In general, the at-home DNA kits help people find long lost relatives by connecting customers — who have chosen to match with close or distant relatives based on shared DNA — with other customers who have also consented to participate in the service.

It’s possible to send a message through the site itself to someone who has shown up as a genetic match.

The DNA tests are not only revealing previously secret information, but in some cases, the results are triggering a whole new round of secrets, as people who learn the long-hidden truth are in turn keeping their knowledge of it secret from the very people who started the secret to begin with.

“Sometimes people get a match that may reveal one of their parents is not their genetic parent, or one of their parents has an additional child,” said Christopher Child, senior genealogist at the New England Historic Genealogical Society , “and they may choose not to bring it up with that relative.’’

The relative may be elderly or frail, he said, making the prospect of such a conversation painful, “but unless they have that conversation, they may never know the situation.”

Other times the relative in question is deceased, he added, and the only one left to question is a widow or widower. “What happens if you bring it up with that person?”

As ever more people upload DNA results for others to see — and are sometimes contacted by strangers who have discovered they are related — all sorts of stress emerge.

In Boston, a woman who sent in a sample of her father’s saliva just for fun, to learn more about her heritage, posted the results and within a few weeks heard from a woman who was a close enough DNA match to be her father’s daughter.

“What a can of worms I opened,” the woman who sent in the sample, an artist in her late 50s, told the Globe, requesting anonymity. “I heard from her during the week that my father was admitted to the hospital with advancing cancer and dementia.”

She never responded, and even now, several years later, her father since deceased, she is still feeling guilty. “I feel bad denying someone trying to find their birth family,” she said. “But what information can I give?”