Gigi Merk was awash with nerves when a Volkswagen Golf pulled up outside a family friend’s home in Toronto.

It was July and Merk, a 17-year-old from Ohio, was about to meet Alyssa Raggio, a 25-year-old Toronto woman she had spent the last three months talking to online and playing video games with.

“I was so nervous when she arrived I didn’t really want to answer the door,” Merk remembers. “I had my mom do it.”

Merk’s jitters weren’t just because it was her first time meeting Raggio. The pair also suspected they were sisters.

It was a hunch Merk uncovered in May after submitting DNA to 23andMe – a company that provides more than 125 reports on ancestry, health predispositions and carriers of medical conditions to customers who pay a fee and mail a tube of their saliva to the California-based business.

When Merk’s results came back, they showed she was a “full sibling” match with Raggio.

“I didn’t think I was going to find anything, so I was pretty shocked and confused,” Merk said.

She didn’t hesitate to fire off a note to Raggio, who answered the next day, but was caught off guard. Raggio had done a 23andMe test almost five years ago in hopes of learning a bit about her medical history, but rarely checked its site anymore and certainly never expected to find a sibling through it.

She had reservations when she first heard from Merk.

“I immediately started running through article after article about 23andMe to see how accurate the match was and what are the odds of it being a mistake,” she said. “Pretty much everyone said that matching on that level wasn’t a mistake… I was shocked.”

And the similarities between Raggio and Merk were hard to ignore, too.

Raggio, who has worked in the human resources sector, had been adopted as a seven-month-old from Jiangxi, China by a Chicago couple and had never been able to learn much about her parents because detailed records of adoptions weren’t kept at the time.

Merk, a high school student and avid soccer player, was adopted in the same Chinese province seven years later at 18 months old by an Ohio couple. She had never met her birth parents, either.

They both like Don’t Starve Together and Tabletop Simulator video games, but hate goat cheese and horror movies.

Plus, it was easy to see the resemblance when comparing their jaw lines, noses and smiles.

It wasn’t long before the pair knew they had to meet, but Raggio couldn’t leave Canada while she was awaiting a work permit, so Merk used a forthcoming trip to nearby Rochester, N.Y. to take a detour to Toronto.

A Merk family friend with a big backyard offered to host the meeting. Raggio’s fiancé Matt drove her there.

“The car ride was unusually silent until the last five minutes. I was pretty much just trying to stay calm as I felt extremely nervous and of course, excited,” she recalled.

“When we arrived, Matt saw someone in the window and (Gigi’s mother Caroline) opened the door with a big smile on her face, before we had a chance to knock.”

Gigi’s mother and father instantly wrapped Raggio in a hug, but Raggio and Merk were still so full of emotions that they only nervously smiled at each other.

But those nerves quickly dissipated and they ended up talking for about four hours. The next day Raggio brought Merk to dinner with her fiancé and maid-of-honour. (Merk said she’ll be at Raggio’s upcoming wedding too.)

They chattered about future visits, their childhoods and even whether the seven-year gap between them means there could be other siblings out there.

Scott Hadly, a 23andMe spokesman, said about 95 per cent of the company’s customers participating in its relatives-matching services end up connecting with a third cousin or closer family member.

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The company doesn’t have data on how often customers have found parents and siblings they didn’t know existed.

“It has happened, but it’s rare and much harder for an adoptee to find a sibling from China,” he said. “They both would have to be somewhere in the U.S. or Canada to be able to take the test and make that match...We don't sell in China.”

And even if relatives are in the same country and using 23andMe, there’s a chance they won’t have opted in to have potential matches with relatives be shared.

23andMe doesn’t make the option automatic to protect user privacy – an issue that has long dogged services like it and AncestryDNA.

There is nothing more personal than DNA, after all, and experts worry about information falling into the wrong hands, being sold to thirtd-parties or being used to target customers with ads.

23andMe has vowed not to share consumer data with public databases, insurance companies, employers, law enforcement or regulatory authorities, unless a court order, subpoena or search warrant is obtained.

However, it does caution on its website that “in the event of a data breach it is possible that your data could be associated with your identity, which could be used against your interests.”

It also warns users that their findings might “be upsetting or cause anxiety” and include things “you may not have the ability to control or change.”

23andMe claims it can detect a myriad of health conditions including risk of lung or liver disease, high cholesterol, a form of adult-onset vision loss, and genetic risk of breast, ovarian and other cancers “based on a limited set of variants.” It also can provide reports on more quirky findings like asparagus odour detection, cilantro taste aversion, hatred of the sound of chewing, ice cream flavour preferences, motion sickness, fear of heights or fear of public speaking.

Hadly said the tests are “very very accurate” and approved by the Food and Drug Administration, which ordered the company in 2013 to “immediately discontinue” marketing its genetic screening service after it failed to provide the U.S. agency with proof that its tests were effective. It has since complied with the FDA’s demands.

Doctors still worry customers will discover potentially-worrisome things about their health through 23andMe and then not know how to handle or move forward with the information.

Those things crossed Raggio’s mind plenty of times, so she read through the terms and conditions carefully and paid attention to privacy settings.

Even if there are concerns with such services, Raggio feels the benefits have outweighed the risks because she found Merk.

“We are both pretty young so we still have a lot of time to get to get to know each other,” said Raggio. “Now if I do want to start searching (for our parents) or she wants to when she’s older, we are not alone and have someone else there.”