I learned a lot about my family in 2019. More than I wanted to.

That spring, I had started a novel about my mother’s uncle and his French lover during World War I. The research took me to France, where I accidentally uncovered my father’s roots in a little town in Alsace whose vineyards and vintages all bear my last name. My oldest daughter and I were treated like family there. It felt like home.

Then, that September, I was uprooted.

A woman in Georgia who had struck a match with me on a DNA ancestry application sent me a message, and I suddenly went from having one brother and one sister to having four half-sisters and four half-brothers.

Evidently, the man I called my father was not, in fact, my father. And at age 67, I suddenly didn’t know exactly who I was or where I came from.

In certain pedantic storytelling circles, it’s called anagnorisis, when a protagonist discovers an unknown family connection, like when a Dickens character realizes that his love interest is his benefactor’s daughter. Or when Darth Vader tells Luke Skywalker, “I am your father.”

In genealogy circles, it’s called NPE, or “non-paternity event.” A 2019 Pew Research study found that approximately 15 percent of Americans have taken commercial genealogy tests, and of those, 27 percent found “close relatives they didn’t know about previously.”

I sent an email to Ancestry.com, asking if they kept statistics on such surprises, and almost immediately got a polite response saying that they didn’t keep that data. I figured they had enough genetic traits and genomes to keep track of without having to think outside the double helix.

But journalist Libby Copeland, who based an entire book on the subject, The Lost Family: How DNA Testing is Upending Who We Are, wrote that the…