What is a NPE?

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Have you heard or read the acronym “NPE”?  Do you want to know what is a NPE and how common it is to see them in a family tree? 

In this post, I will answer all of these questions about NPEs, also known as non-paternity events, and more!

I discovered an potential NPE in my own family tree, which is what got me thinking about this topic. It turns out that one of my grandfather’s aunts, the older sister of his mother who he loved very much, was not the child of the person who was in my family tree listed as her father.

We discovered this particular NPE through DNA testing, since my father didn’t share enough DNA with his second cousin for it to be a “full” relationship.

What is an NPE?

NPE stands for a “non-paternity event”.  Non-paternity event means that the person who is assumed to be the father, usually the husband or partner of the mother, is not the biological father. 

The term NPE is not usually used in relation to adoption or step-parent situations. In cases such as these, the key individuals involved, most importantly those raising the child, generally know that the step parent or adoptive parent is not the biological parent.

Non-paternity events (NPEs) are also sometimes called mis-attributed paternity, not parent expected, or paternal discrepancy.  No matter which words you choose to describe the situation, it means one thing: paternity has been incorrectly assigned to the wrong male.

Sometimes, a person who was adopted might not be aware that they were adopted, and this person or their descendants might use the term “NPE” to describe the situation when they realize that their DNA results don’t show what they expected to see. 

The NPE that I have mentioned towards the beginning of this post from my family tree occurred very long ago. My grandfather’s favorite aunt was born in 1898, after all, and so it is ancient family history.

Everyone involved has long since passed away, and so I can’t say for sure whether it was a secret to everyone, or whether it was common knowledge that didn’t get passed down to future generations. My great-great grandmother was very pregnant when she married my great-great grandfather, and so I believe that he likely knew that someone else was the father.

Update: I have since been in touch with a granddaughter of this relative, and she is aware of the identity of her grandmother’s father. This means that her grandmother must have known, but we still are not sure if the rest of her siblings were aware.

How are most NPEs discovered?

Many people discover that there was a non paternity event in their family tree through DNA testing and genetic genealogy.

It’s important to note that DNA matches are the only aspect of autosomal DNA test results that can provide evidence of or dispute a theory of a NPE. Ethnicity estimates cannot be used as evidence to prove or dispute paternity.

In addition, we should also acknowledge that informal adoptions occurred frequently in the past, and sometimes the immediate or extended family was not aware of the adoption.  Since no one discussed the adoption, and the adopted child was raised as a biological child, descendants of this adopted child would not be aware of their true biological lineage.

With the advent of modern DNA testing, evidence of these adoptions comes to light.  So, sometimes a perceived “NPE” was not the result of any sort of dishonesty or deception, we just don’t always have all of the information.

How common are non-paternity events?

People are often surprised to learn about how common it is for a father to unknowingly raise a child, or assign his paternity to a child, that is not his in a biological sense.  It’s impossible to know exactly how many children are born to NPE situations, but lots of studies have been performed to try to figure out an average rate.

How do researchers figure out whether an NPE has occurred?  For modern populations (i.e. you and me), researchers are able to do studies of sample populations and actually perform paternity tests across the families in order to determine paternity (or non-paternity).

Other researchers focus on male lines of family trees, since men generally carry their expected father’s surnames, and use Y DNA testing to verify their hapologroup and Y DNA matches. 

Still others, experts in genetic genealogy, are able to perform studies using autosomal DNA (the kind of test that Ancestry DNA and 23 and Me perform) to determine whether or not the known family tree matches the DNA results.

For example, we have a lot of data that shows us an expected range of shared DNA (measured in centimorgans) between relatives of a particular relationship type. When the shared DNA amount doesn’t match up, we start to think about a possible NPE having occurred.

But, let’s get back to what you really want to know.  How common is this, really? 

Some of us prefer to believe that it has never, ever occurred in our family, while the more cynical among us might think that a NPE in genealogy is more common than correctly attributed paternity. 

In reality, NPEs have likely occurred in all of our families – and maybe more commonly than we might think, but not so much to make genealogy a hopeless endeavor.

Below are some interesting conclusions that can be drawn from several studies:

Less than 5% of births are NPEs, on average

The average rate of NPEs is less than 10%, and likely no higher than an average of 4%.  In other words, as many as 1 in 10 births might be incorrectly attributed to the wrong father, but it’s most likely that only about 1 in 25 births fall into this circumstance.

NPEs rates vary in across cultures

The actual rate of NPE can vary across time, culture, and geography, which means that there might be a slightly higher percentage of NPEs in some places (and not always the places that you would expect) and lower in others.

The father’s confidence matters

When there is “high paternal confidence” (meaning that the father feels very confident that he is the biological father of his child), there is a much lower percentage of NPEs than average – about 2%, or less than 1 birth out of 50 – pretty low odds!

When there is “low paternal confidence” (meaning that the father feels like there is a good chance that he is not the biological father of the child), the NPE rate can be as high as 30%.  This makes sense, however, since a lot of people who do paternity testing do it because they know that there might be a chance that there is a NPE, or they are unsure.  

We can assume that most of the time when a father assigns his last name to a child, especially within a marriage, that he assumes that the child is biologically his and has “high paternal confidence”.

You may or may not have an NPE in your family tree

People who are really into statistics might be tempted to extrapolate these numbers to help make general conclusions about how accurate the average family tree might be. In the case of non-paternity event statistics, it could lead us to assume that there are many births in our family tree that are attributed to the wrong male ancestor.

The assumption that all of our known ancestors are truly our ancestors has an important effect in genealogy. After all, we research our family tree to learn about our ancestors, and it is quite a shock to think that we may not be descended from some of the people that we spend so much time learning about.

Except in a tree where there is pedigree collapse, everyone has 64 individual great-great-great-great grandparents. If we assume that 4-10% of those ancestors are the result of mis-attributed paternity, or a non-paternity event, then that means that we have between 3-6 ancestors in our tree in those spots that don’t belong there.

Is this the case in every family? In reality, it’s impossible to say based only on the very general average rates of NPEs that I mentioned above how likely it is that they have occurred in significant numbers in your family tree.

The basic takeaway for a genealogist, or a genetic genealogist, would be to keep in mind that NPEs do happen and have occurred, and to make sure that DNA evidence backs up family tree research. There are some good techniques that can be used using data from our DNA results, such as the analysis of DNA matches and chromosome mapping using tools like DNA Painter.

Note:  DNA testing companies offer ethnicity estimates along with DNA matches.  Ethnicity estimates cannot and should not be used as evidence of a non-paternity event, nor should they be used to determine paternity.  DNA matches, on the other hand, can be quite useful for this purpose.

Conclusion

I hope that this post helped you understand what a NPE is, and how common it might be – or might not be.  I’d love to hear your thoughts on this topic, especially if you have any questions or would like to share your own experience discovering a NPE in your own family tree.

Thanks for stopping by today!

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