(Bloomberg) –If you’re a fan of genealogy television shows, that DNA test you might receive for the holidays can be the best way of opening up a wealth of information about you and your ancestors. Or if you’re like me, it can bring unexpected, life-altering news.

My DNA test, taken in early 2018, showed my mother gave birth to a baby boy in 1958, seven years before I came along, who was then put up for adoption. His new parents named him Richard. Any doubts I had were squashed when I got my first look at a photo of him. I saw myself staring back at me.

So think long and hard when deciding whether to share the intimate code that defines who you are, as you may find yourself facing huge emotional issues from which you may never get closure.

You may find that previous generations weren’t honest about their relationships. Religions can be called into question, and some people may not relish being saddled with health-related details, including tendencies for rare cancers or early-onset Alzheimer’s. There’s always the chance the information doesn’t add up: My test suggested I’m predisposed to consume less caffeine. It is wrong.

My own experiences have been complex but mostly a joy. They’ve helped me make sense of my past and the forces that shaped my mother’s own troubled life, which ended much too soon in 1992 after years of alcoholism and addiction. I love my new extended family and have found a sense of peace that was lacking in my life. Almost.

Richard died in 1996, possibly from an aggressive cancer triggered by his exposure to toxins in Operation Desert Storm when he served as a captain in the U.S. Marines. His passing robbed me of a chance at a fraternal bonding that as an only child I clearly had longed for over my life without realizing it.

Internal Clocks

After spending time with his family, I’ve been able to draw a portrait of his personality that is in many ways eerily similar to my own, with shared habits, emotions and desires. We couldn’t be less similar in how we were raised, but our internal clocks appear closely aligned.

Based on the number of articles I’ve read about DNA tests producing unexpected results, my experience may not be so unusual, especially as the popularity of DNA testing has expanded. There’s a Reddit devoted to the subject and I was able to find three people in my Facebook feed who had discovered oddities in their test. One woman told me she had discovered that she was adopted and that her parents hadn’t told her. Another developed a relationship with her half sister but was cruelly rebuffed by their birth mother.

23andMe, the Sunnyvale, California-based company that I selected for the DNA test, says they don’t have data for how many people have discovered surprising results but Christine Pai, a communications manager for the company, tells me they’ve trained their customer representatives to help panicked callers come to terms with their discoveries.

The choice to share your data takes about as long as accepting the terms and conditions in a piece of software, though 23andMe and other services say they give ample warning to all their customers.

Read the manual and remember: a DNA testing service is offering up only data — it has no feelings. So it’s not about the tech but what you choose to do with it. Relatives and loved ones may not be able to clear up any mysteries you encounter.

Precious Secret

After my discovery, I hurriedly called up the few remaining relatives who might have known something. I pictured them holding this precious secret all those years and the revelation that would follow. All I got were stunned silences. “The biggest mystery since the JFK assassination,” one cousin remarked.

For most, the DNA results will be but a blip in your day, a new topic of conversation at your next dinner party and another piece of information that can be tossed into a box with the family photos and passed down to the next generation. As for myself, I’ve spent the time adjusting, learning to live with my new circumstances and using the time to probe deeply into my past in hopes of understanding myself better.

But as many boxes as I open in my attic of photos from the past, I will not find what I’m looking for, a picture of me and my brother together. Not even 23andMe’s test can make that happen.

(Douglas Lytle is an editor with Bloomberg Intelligence in London.)