How Can DNA Identify an Unknown Grandfather?
DNA testing can sometimes help identify an unknown grandfather even when traditional records do not provide his name.
The process usually does not involve finding a DNA match labeled “your grandfather.” Instead, genealogical DNA research examines groups of genetic matches, their family trees, shared ancestors, locations, ages, and relationships. Those clues can be combined with traditional genealogical records to identify families—and eventually individuals—who may fit the unknown position in the family tree.
What Type of DNA Test Can Help?
For most unknown-grandparent research, autosomal DNA is the primary starting point.
Autosomal DNA is the type of test offered by the major consumer DNA testing companies. It compares portions of your DNA with other people who have tested and identifies individuals who share DNA with you.
Generally, closer relatives share more DNA than distant relatives. However, the amount of shared DNA can correspond to several possible relationships, so a DNA match usually cannot be identified solely from the amount of DNA shared.
The match must be evaluated within the larger family structure.
Who Should Take the DNA Test?
Whenever possible, the person who is closest genetically to the unknown grandfather should test.
For example, if the unknown man was your grandfather and your parent who was his child is living and willing to test, your parent's DNA will usually provide stronger evidence than yours because your parent is one generation closer.
If that parent is unavailable, your own DNA may still provide useful evidence.
Other relatives can also be valuable. Siblings, aunts, uncles, cousins, and other descendants may have inherited pieces of DNA that you did not inherit.
Having more than one appropriate relative tested can sometimes make it easier to separate DNA matches belonging to different branches of the family.
How Do DNA Matches Point to an Unknown Family?
The first step is often determining which DNA matches belong to family lines that are already known.
If matches can be associated with your mother's family, for example, they may be separated from matches connected to your father's family. Known paternal or maternal relatives can provide valuable reference points.
Researchers can then examine the remaining unexplained matches.
Rather than concentrating on a single match, the goal is often to identify groups of matches who are related to one another.
If several DNA matches descend from the same ancestral couple or family, that family may provide an important clue to the identity of the unknown grandfather.
Why Are Shared Matches Important?
Shared matches are people who share DNA with both you and another DNA match.
Suppose you have a DNA match named Susan. When you examine the people who match both you and Susan, several of them may descend from the same family.
That pattern can indicate that the DNA you share with those individuals came from a common ancestral line.
By repeating this process with multiple matches, researchers can begin separating matches into family groups.
These groups can sometimes lead to the family of an unknown ancestor even when none of the individual matches is a particularly close relative.
What If My DNA Matches Don't Have Family Trees?
This is a common problem.
Some DNA testers have extensive family trees attached to their results. Others have very small trees—or no tree at all.
A missing tree does not necessarily make the match useless.
Traditional genealogy research may be used to reconstruct the ancestry of an important DNA match using records such as:
Census records
Birth and death records
Marriage records
Obituaries
Newspapers
Cemetery records
Probate records
Public family trees used as research clues
Other historical records
By determining who a DNA match's parents and grandparents were, it may become possible to connect that person to other matches and identify a common ancestral family.
How Do You Go From a Family to a Specific Man?
Identifying the correct family is only part of the process.
Once DNA evidence points toward a particular family, traditional genealogical research becomes especially important.
Potential candidates can be evaluated by considering factors such as age, location, family relationships, migration patterns, occupations, military service, and other historical evidence.
For example, if the unknown grandfather must have been an adult living in a particular city in 1945, researchers can examine men from the identified family who were the appropriate age and determine which ones could reasonably have been in that location.
Some candidates can be eliminated. Others may require additional research.
The objective is to find the individual who best fits both the genetic evidence and the historical evidence.
Can DNA Prove Who My Grandfather Was?
Sometimes DNA evidence can become very strong, particularly when multiple independent DNA matches connect to both sides of the suspected grandfather's family.
In other cases, the evidence may narrow the possibilities to a particular family or a small number of candidates without conclusively identifying one individual.
The strength of the conclusion depends on the available DNA matches, the relationships between those matches, the quality of their family trees, available historical records, and whether additional relatives are available for testing.
DNA evidence should therefore be evaluated together with documentary evidence rather than treated as a single definitive answer.
What Information Is Helpful Before Starting?
You do not need to know much about the unknown grandfather to begin, but anything already known can help.
Useful information may include:
The name of his child
Approximate conception or birth dates
Where the child's mother lived
Places where the family lived
Possible names or family stories
Photographs or letters
Known relatives
Existing family trees
DNA testing company
Information about significant DNA matches
Even uncertain information should be identified as such rather than discarded. A family story may provide a useful clue even if later research shows that some details were incorrect.
Will You Contact My DNA Matches?
DNA research does not automatically require contacting close DNA matches.
At KB Family History, research can begin by analyzing the information and DNA results available to you, along with genealogical and historical records.
Any potential contact with another person should be discussed with you first. A researcher should not unexpectedly contact close DNA matches or biological relatives on your behalf without your knowledge and permission.
What If the Unknown Grandfather Is Deceased?
DNA research can still be effective even if the person being identified died many years ago and never took a DNA test.
You may share DNA with his descendants, siblings' descendants, cousins, or other relatives.
Those matches can provide genetic links to different branches of his family.
In many cases, identifying an unknown ancestor involves reconstructing the family through the DNA of living relatives rather than obtaining DNA directly from the person being identified.
How Long Does DNA Identification Take?
There is no standard amount of time.
Some cases contain close DNA matches with well-developed family trees and can produce useful leads relatively quickly. Other cases require reconstructing several family trees, analyzing many distant matches, separating multiple family lines, or researching families across different locations.
New DNA matches can also appear as additional people test.
For that reason, DNA identification should be treated as a research process rather than a guaranteed instant answer.
Ready to Investigate an Unknown Grandfather?
If DNA testing has left you with more questions than answers, professional DNA and genealogical research may help organize the evidence and determine what your matches are telling you.
KB Family History offers DNA research through Understand My DNA and more focused biological-family identification through Find a Biological Parent or Relative.
You can begin with the DNA results and family information you already have. You do not need to understand centimorgans, shared matches, or genetic relationships before submitting a research request.