A DNA match tells you that two people share ancestry, but it does not tell you who the shared ancestor was. Turning a match into a documented relationship requires records, and French records are among the best in the world for the job. This guide gives a step-by-step method for taking a match from the DNA site to a named ancestor in a French register.
The principle: DNA suggests, records prove
A shared DNA segment shows that you and your match descend from a common ancestor somewhere. The records show who that ancestor was, and confirm each link between you. Treat DNA as a lead and the registers as the proof. A relationship is not established until you can document it generation by generation.
Step 1: Know your own line
Before you analyze a match, document your own family as far back as you can, ideally to a French commune. See our complete guide to tracing French ancestry and our guide to finding the commune of origin.
Step 2: Study the match
- Note the amount of shared DNA and the longest segment.
- Read the match’s tree, if there is one, and look for French surnames and places.
- Check shared matches, to see which of your known relatives also match this person.
- Estimate the likely relationship, remembering that the figures give a range, not a fixed answer.
Step 3: Find the likely common ancestor
Compare your tree and the match’s tree, and look for a surname, a commune, or a couple that appears in both. Often the match’s tree stops short, so you will build the connecting branch yourself. A service that combines trees, records, and DNA, such as MyHeritage with its French records from Filae, can suggest record matches and possible connections, which you then verify. Treat every suggestion as a hypothesis.
Step 4: Confirm in French records
- Take the suspected ancestral couple to the departmental archives and find their marriage. See our archives guide.
- Read the marriage act to confirm the couple’s parents, and use état civil for the nineteenth century and parish registers before 1792.
- Trace the descendants of the couple down to you, and down to your match, citing each record.
- Check that both lines meet at the same documented couple.
- Record the register, page or image number, and date consulted for every link.
Step 5: Check the DNA against the paper trail
Once you have a documented relationship, check that the amount of shared DNA fits. If it fits, the match supports your tree. If the DNA is much higher or lower than expected, look for a second relationship or an error. The two sources keep each other honest.
Common mistakes
- Trusting online trees. Many trees copy each other’s errors. Verify every link in the original register.
- Stopping at the first plausible ancestor. A match may connect through a different couple than you expect.
- Ignoring spelling variants. See our spelling variants guide.
- Using ethnicity percentages as evidence. They are estimates. See French DNA ethnicity estimates explained.
- Assuming a very common surname proves a link. See the most common French surnames.
When the records and the DNA disagree
If your documented tree and your DNA disagree, pause and look for reasons: an undocumented adoption, an unrecorded father, a name change, a mixed-up record, or a second connection through another line. Handle surprises with care, and treat relatives’ privacy with respect. Find more help in our guide to finding French cousins with DNA.
Illustrative composite (not a real family): A researcher in Louisiana shares 78 cM with a match whose tree lists a village in Normandy. By comparing trees, she identifies a possible couple married in 1851. The marriage act in the departmental archives names both sets of parents, and tracing their children confirms that her ancestor and the match’s ancestor were brothers.
For the comparison of tests, see our best DNA test for French ancestry, and see the DNA hub for an overview.
A worked example in detail
Illustrative composite (not a real family): A researcher in Wisconsin shares 95 cM with a match who lists ancestors from a village in Lorraine. Both trees contain the surname Thiriet and the same département. She builds the match’s tree back two generations from public records and finds a Thiriet couple who married in 1862. In the departmental archives she reads the marriage act, which names the groom’s parents and a witness who is the bride’s uncle. Tracing the couple’s children forward, she finds that her great-grandfather and the match’s grandmother were siblings. The amount of shared DNA fits second cousins once removed, so the DNA and the documents agree.
Tools that help
- A name index such as the one on MyHeritage, which draws on Filae’s French records, to find acts across communes.
- The departmental archives for original register images. See our guide.
- A spreadsheet to log matches, amounts of DNA, suspected ancestors, and the records that confirm each link.
- Reference tables of shared DNA and relationships, as compared in ISOGG’s autosomal DNA testing comparison chart.
Documenting your conclusion
When you reach a conclusion, write it down in a form someone else could check. State the relationship, list the records that prove each link, with the register, page or image number, and note the amount of shared DNA and whether it fits. If the evidence is incomplete, say so and list what is missing. A clear write-up protects you from repeating work, helps cousins verify your tree, and shows you quickly where the next gap lies.
Triangulation in plain language
Triangulation means finding three or more people who share the same segment of DNA and who all descend from the same documented ancestor. It is stronger evidence than a single match, because it shows that a particular stretch of DNA came from a particular ancestral couple. Chromosome browsers and tools such as GEDmatch support it. In France, where the pool of testers is small, even one well-documented triangulated group is a significant result.
For official background on French records, consult the FamilySearch Research Wiki on France and our French genealogy records hub.
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