“Not parent expected” – NPE – is a surprise that thousands of us have gotten as a result of consumer ancestry DNA testing. We discover that we are the offspring of a sperm donor, or sexual violence, or a long-ago fuzzy night at a party, a brief interval between partners, an affair, or a single experimental partner-swap long forgotten.

We find out that we aren’t who we thought we were, at least in our genes. I know I’m the same person, of course, but something has changed.

DNA Day to me this year means that I share approximately 25% of the DNA signposts used to assess ancestry – some 700,000 or so data points that mark genetic diversity – with six half-siblings, and possibly more.

I haven’t written about it much, because I can’t. My mind goes in too many directions, contemplating the complex repercussions. And so I’ve mostly shared my story with others who can more objectively tell it, the journalists who contacted me after reading one of my posts: a newspaper reporter, the author of an upcoming book on NPEs, and a film crew for a documentary on genetic testing.

My feelings have evolved. I’m calmer now.

It started in early September, when I heard from a woman who was initially listed as a first cousin on Ancestry.com. I’ve since learned that the half-sib matches often start out that way, both because the ranges of shared markers overlap, and perhaps to slow the avalanche of unexpected information.

In October I looked closely at the data and realized that she and I share nearly as much DNA as do full siblings. We are certainly halfsies. Then after December, in the wake of the massive holiday advertising campaign, matches began to pour in.

I was left with the six half-siblings, and soon after confirmation that the sister I grew up with is indeed a full sibling, although I never doubted that.

Of the six half-siblings, I’ve met two, been in touch with two others, and it is possible that the other two do not even know that they are part of our little kin club. Their adult children and perhaps nieces and nephews are in denial or want to protect them from knowing, or both. I respect that and don’t stalk them through Facebook as it is all-too-easy to do.

One of the six is the “social” offspring of the donor. We can deduce this from the list of relatives and the ways we can be related. I’d share 25% of the surveyed DNA  with a half-sister and 12.5% with her children, but not with the children of her siblings, who presumably have a different father. But when I’m matched to a half-sibling as well as his or her nieces and nephews and more distant relatives, that points to the extended donor family.

From there, what to do becomes a question of ethics. Should a donor’s right to privacy or a recipient’s right to know her origins prevail? I don’t have an answer for that. I’m willing to step back, not pursue it, perhaps because I’m older. If I were 30 matters might be different; I’d want to know my medical history and possible future. Personal opinions vary.  

What about the rights of the sperm donors who had been promised an anonymity that is no longer possible in this day of spit-in-a-tube time machines? Guido Pennings, professor of ethics and bioethics at Ghent University in Belgium, just published a paper arguing for protecting donor anonymity that has had the folks on  NPE and Donor Conceived private Facebook groups up in arms, and understandably so. The flip side is the effect of the news on the donor’s wife and social children. I’ll be weighing in on this next week for Genetic Literacy Project.

My story has had a happy, if confused, not-quite-finished ending. I no longer check Ancestry and 23andMe every day — maybe once a week. I don’t think about the weirdness every day anymore. I’ve met a few terrific people with whom I share quite a bit of my DNA. I have new friends, and that’s always a good thing. 

But in honor of this DNA Day, I urge the testing companies to take some steps back and tamp down the advertising. Mother’s Day has been and will be upsetting enough; Father’s Day is going to be much worse because of the inherent difference between the male and female gametes. That is, a sperm donation can go much farther than an egg donation, sometimes generating dozens and even more than 100 half-siblings. So please put aside the quest to make money and to provide entertainment and consider that DNA ancestry findings can devastate families.