Most NPEs in genealogy are the result of either a hidden (undocumented) adoption, meaning an adoption that was kept secret — or was simply unofficial — and for which no paper record has been found, or an illicit relationship on the part of the mother, also kept secret.  In other words, these are events totally unsuspected by genealogists working decades or centuries later.  More recent NPEs can be created via sperm donation, egg implantation, and other means, but these are seldom issues in genealogy where the NPEs are in the past, if not the distant past.  Widespread DNA testing is uncovering these events, often to the dismay of the family genealogist, not to mention the individual tested.

You may encounter genealogists using NPE with a somewhat different meaning.  Paper genealogists may consider an adopted child an NPE, even though his adoption is known and the identity of his biological father is known, because he would be an NPE to his "social father."  They would also consider a stepfather to be an NPE, and they might also consider a bad paper connection between a father and child to be an NPE, once the mistake is uncovered. 

Genetic genealogists tend to use NPE with a more restricted meaning.  In this narrower meaning, an adopted child is not an NPE if the fact that the child is adopted is known, nor would they consider a mistake in paper genealogy uncovered by DNA testing an NPE — they would simply consider it bad genealogy.  For those doing genetic genealogy, the term, "NPE," is usually restricted to cases where the paper genealogy is seemingly correct, but is contradicted by DNA test results.  These cases are going to be either a hidden adoption or an illicit relationship on the part of a wife.

Keep in mind that, before the late 20th Century, adoptions were usually kept secret, frequently because the child was born of an unwed mother and being a bastard child carried a severe social stigma.  Even well into the 20th Century, it was also generally believed to be psychologically damaging for the child to be aware that he or she was adopted, so a child was apt to never be told they had been adopted.  As for extra-marital relationships, not much has changed with regard to the desire of the wandering spouse to keep the relationship secret.  What is different is that, in the past, the family's fear of scandal was likely to lead to the affair being hushed up and the marriage remaining intact, at least superficially, while today an extra-marital affair can more easily lead to divorce.

Another common occurrence is the child of a young unwed mother being raised as the child of her own mother, that is, as her own sibling.  These often appear in the censuses as a child too young to be that of the alleged mother.  Some novice genealogists accept the birth of children to mothers in their late 40s and early 50s, as shown in censuses, but these cases really need to be viewed with skepticism because most women have had their last child by the age of 43, if not sooner.  In the case of male children, there is some hope of using Y-DNA testing to clarifly the situation if a patrilineal male descendant can be found and tested — except in those grim cases where the father of the illegitimate child is the father of the unwed mother, or some other close male relative, a situation likely to have been kept very secret.  The bottom line is that cultural conditions in the past were conducive to generating NPEs.

The "NPE rate" in my surname projects is running about 10%, that is, about one man in ten who is Y-DNA tested turns up with an NPE, which is the reason I advocate all men interested in their genealogy begin their research with a Y-DNA test.

While it may seem that an NPE is an unmitigated genealogical disaster, with the aid of DNA testing (see Strategy for Locating an NPE), it is possible to unravel them to some degree or another.  To illustrate what is possible, given below are brief descriptions of some of the NPEs revealed in the Y-DNA surname projects I administer, including the extent to which they've been resolved, so far.

Ira CORBIN was born in Massachusetts, and he died in South Carolina.  With Ira being from Massachusetts, it was expected his descendant would be a DNA match to tested descendants of Clement CORBIN, the major progenitor of CORBIN in New England.  Results revealed there was no possibility of a connection because Clement's descendants are Haplogroup G2a and Ira's descendant is Haplogroup R1b.

Ira's descendant is, however, a tight genetic match with a well-known New England SHERMAN family.  There are, in fact, several marriages in New England and New York between these SHERMANs and the descendants of Clement CORBIN, so Ira's paper ancestor will probably turn out to be one of them.

Until we have enough cousins of this individual tested, we won't know where in his lineage the NPE took place, but there does seem little doubt that it occurred in New England, where these two families were interacting, because these SHERMANs are notably absent from SC.  We may also have uncovered the reason Ira left Massachusetts.

Wilmer ROBISON was the child of Rebecca A. STEPHENS, daughter of Joshua STEPHENS & Caroline CORBIN.  Wilmer was born out of wedlock, before Rebecca's marriage to Benjamin Harrison ROBISON, who later adopted Wilmer and gave him his name.  Family legend was that Wilmer was the product of a relationship between Rebecca and her first cousin, Elmer Ellsworth CORBIN, a descendant of the Clement CORBIN mentioned above.  Testing of a patrilineal male descendant of Wilmer revealed that he could not be a descendant of Clement because, as above, he is Haplogroup R1b, not G2a.  His results did reveal, however, that he is genetically a STEPHENS.

It appears that Rebecca didn't have an affair with one of her CORBIN cousins, but with one of her STEPHENS cousins — or the darker interpretation that she was abused by one of her STEPHENS relatives.  However, Rebecca was an adult when Wilmer was conceived making the latter seem unlikely.  So, as it turns out, instead of having a double dose of CORBIN genes, this individual has a double dose of STEPHENS genes. 

Because all of Rebecca's near STEPHENS kin will likely have the exact same Y-DNA test results, it's unlikely that Wilmer's actual father will be identified, unless court records can be found of a bastardy claim or assignment of a guardian.  This testing did accomplish something else, though. 

Prior to this test, they did not know which STEPHENS family they were part of, making this the first time in my experience that Y-DNA testing of a son identified the patrilineal origin of the mother!

Jacob STROUP II is, on paper, the eldest son of Adam STROUP, son of Jacob STROUP I, son of Johann Pieter STRAUB, 1733 immigrant to Philadelphia, PA.  The problem is that the four tested descendants of Jacob II (each through a different son) are Haplogroup J2, so are not a genetic match with the descendants of the other descendants of Johann Pieter STRAUB, who are all Haplogroup I1. 

These descendants of Jacob II are, however, a close DNA match with the BIDDLE descendants of Andreas BÜTTEL, 1752 immigrant to Philadelphia, and in fact, the two families can be found together early in their history in PA and MD.  The exact paper connection has yet to be made, but there is no doubt that there is a genetic one.

The paper connection from Jacob II to Adam does seem sound (on a deed, Jacob names his father as Adam).  Given that Jacob II is Adam's eldest child, the most likely explanation is that Jacob was a child from a prior marriage of Adam's wife, Catherine.  Unfortunately, the lack of extant early marriage records greatly hampers the resolution of this NPE.

It is not yet known where in the patrilineal line of descent from Silas BELEW to the test subject the NPE occurred, but we know one did occur because the testee is genetically a STROUP.  Examining the evidence, we find that, in the 1850 census, Silas BELEW was listed next to Harmon STROUP, a member of this particular STROUP family.  We also continue to find relationships between these STROUPs and BELEWs for the following censuses up through 1930.  Further testing of cousins could pinpoint the generation in which the NPE occurred, and deeper research in county court records might produce guardianship records or a bastardy claim that could resolve this NPE entirely.

Even before a patrilineal descendant of Jacob Jackson STROUP was DNA tested, I had suspected he was adopted because he and a sister, Mary, appeared late in the marriage of their parents, Jacob & Mary (KETTERING) STROUP.  This suspicion was supported when Jacob's patrilineal descendant turned out not to be a DNA match with these STROUPs, but instead, to be a tight genetic match with a German NEUHAUS / NEWHOUSE family.

An examination of county records revealed a deed showing the STROUP and NEWHOUSE families owned adjacent land in Wythe County.  Evidence further shows that the only NEWHOUSE living in the area at the time Jacob was conceived was John NEWHOUSE, and that John's first wife died about the time Jacob was born or within a year or two afterwards.  John NEWHOUSE then left the state and remarried, with no children from his prior marriage evident in his new household.

There seem to be two most likely possibilities:  1) that the childless STROUP couple adopted John's child (or children if Mary is, indeed, Jacob Jackson's sister) after John's first wife died, or 2) that John NEWHOUSE had an affair with Mary (KETTERING) STROUP, which would also mean the couple's infertility was caused by Jacob, not Mary.  If there was a legal adoption and if county records are extant, it may be possible to find a record of the adoption or the assignment of a legal guardian.

This individual descends from William Waitsel CRUMP, son of unwed mother, Rebecca CRUMP, who sued Waightstill PRESTWOOD for bastardy over the birth of William in 1878 in Caldwell Co., NC.  We would have expected William's patrilineal descendant to possess a PRESTWOOD Y-chromosome, but it turns out he is a 66/67 match with the STROUPs of Gaston Co., NC.  It appears the NPE must have occurred later, after Rebecca had left Caldwell County (where there were no STROUPs) and settled in Gaston County (where there was an abundance of STROUPs), but it will take some testing of cousins to pinpoint the individual who first bears the STROUP Y-chromosome.  Update:  his father has now been tested, and he, too, is a match with STROUP.

Six paper descendants of Peter CORBIN of Pickins Co., SC, are a close match with each other, but a seventh is not.  The seventh does, however, have a 67/67 match with a FIELDS family.

Even though a paper connection has never been made, based on his migration path and very rare surname, Charles CARRICO of Maryland (then Washington Co., KY, then Sullivan Co., IN) has always been assumed to descend from Peter CARRICO, 1674 immigrant to Maryland.  DNA testing of descendants through sons Josiah and Basil now supports that Charles is, indeed, descended from Peter.  However, testing of two brothers descended through Charles's paper son, Reason CARRICO, are not a match to the other descendants of Charles.  One of these brothers has been tested to 67 markers, and he does have a 36/37 match with a MAJORS and a 63/67 match with a LITTLETON.   Update:  the CARRICO and LITTLETON upgraded to 111 markers, and their match remains borderline (i.e., their common ancestor may have been pre-surname adoption).

This NPE does resolve a long-standing issue over the fact that Reason's birthdate of 8 Feb 1794 is too closely spaced with his brother Basil's birthdate of 11 May 1794.  It may be that what we have uncovered is support for Reason having been adopted, while putting to rest the issue of the birthdates being too closely spaced.  The fact that Charles's wife was Martha REASON strongly suggests Reason CARRICO is her kin (a nephew, perhaps?).  We are still seeking a male REASON related to Martha for Y-DNA testing. 

On paper, this individual descends from William BIDDLE (1630-1712) of London, England, and Burlington Co., NJ, yet he does not match another descendant of this same William.  He does, however, have a strong match (65/67) with a LETT whose earliest ancestor was of Mecklenburg Co., VA.  The LETT does not believe the families have crossed paths, at least not in the U.S.  I recommend our BIDDLE begin his unraveling of this match by testing cousins (viz., a 1st cousin, then a 2nd, then a 3rd, etc.), until he locates in which generation the NPE occurred.

Lawson Sidney STROUP was born out of wedlock to Elizabeth STROUP, a member of the well-known and prolific STROUP family of Gaston County, North Carolina.  Not surprisingly, a patrilineal descendant of Lawson is not a Y-DNA match with these STROUPs.  We do find that he has a match with three surnames:  two 12/12 matches with SELLERS, one 25/25 match with a QUEEN, and one 36/37 match with a COPE.  Their haplotype is rare (unique just to them), and it appears (for reasons given on Lawson's page, linked above) that all five are actually SELLERS.

An examination of the 1880 census shows a young, unmarried Elizabeth STROUP living with her parents in Gaston Co., NC, surrounded by SELLERS households.  These SELLERS are all descended from a well-known German SÖLLERS / SOELLERS / SELLERS progenitor, with which our subject is a DNA match.  Unless there is an extant bastardy claim by Elizabeth in the county court, it is unlikely the actual father of Lawson will be identified, but there can be no doubt where his patrilineal ancestry lies.

I urge the QUEEN and the two SELLERS to upgrade to 37 markers to solidify the match, though their haplotype is sufficiently rare that I don't doubt all five have a common ancestor.  Their common ground appears to be North Carolina, and when I have time (ha!) to extract their census records, I'll be looking to see exactly where the COPE and QUEEN lines crossed paths with the SELLERS.

This individual descends from John A. CORBIN, son of an unmarried Amanda CORBIN, one of the Pickens Co., SC, CORBINs.  Not surprisingly, he's not a match for Amanda's CORBIN kin.  He is, however, a match with a WOODRING (= WOTRING/VAUTRIN).

Interestingly, we find Amanda CORBIN listed next to one of these WOODRINGs in the 1900 census of Gilmer Co., GA, not long after her son was born.  If this WOODRING isn't John's father, then some WOODRING closely related to him is.

I can't say I recall having an NPE resolve itself so quickly, but it does seem we have the answer.  And I guess if you're going to get one, it might as well be with a well known family that has "crossed the pond."  These WOODRINGs descend from Paul VAUTRIN (c1570-1633) of Alsace, France.