I was just curious to see if I would find anything a bit interesting, Greenberg says.

As Greenberg and the other woman began communicating, their shared story took shape.

Then I started getting panicky emails from her, Greenberg says.

Which DNA Databases Are the Best and Worst for Privacy?

And just like that, Greenberg lost the half-sister she never knew she had.

Im really frustrated, says Greenberg, achild and family psychologist in Connecticut.

Im a curious person who loves peoples life stories.

Greenbergs case is certainly not an isolated incident.

And as the DNA databases continue to grow by the millions, more of these stories will be told.

Im sensitive to feeling rejected; thats a trigger for me, Greenberg says.

Thats the isolating experience Shapiro found herself in.

There were so few people left.

My dads ninety-three-year-old sister, Shirley, was one, but I couldnt possibly call her.

If my father wasnt my father, then she wasnt my aunt.

The thought made me tremble, and I lowered myself into a plastic chair bolted to the floor.

Grandparents, uncles, aunts, cousins floated away from me like dozens of life rafts.

Consider how you might pursue the truth if you didnt have anyone you could rely on for real answers.

Once one of these databases has your information, it stays there indefinitely.

Consider whether youre okay with that sort of thing looming in the background.

Be prepared for disappointment

Disappointment can come in many forms with these results.

Or it can be big (as weve already discussed).

For more from Lifehacker, be sure to follow us on Instagram@lifehackerdotcom.