Learn
Genetic genealogy, explained properly
Four core concepts carry almost every conversation about DNA matches. Get these right and the calculators stop being magic boxes.
What Is a Centimorgan?
The unit behind every shared-DNA number — and why it is not a percentage.
8 min read
Autosomal DNA Explained
What autosomal testing can and cannot tell you about your family.
9 min read
DNA Segments and Why They Matter
Half-identical regions, segment size, and the difference between one big segment and many small ones.
8 min read
Triangulation for Genealogists
Using three-way segment overlap to tie a match to a specific ancestral line.
9 min read
Relationship guides
Deep dives on the specific relationships people most often need to identify.
First cousin
Roughly 850 cM, and four neighbours that sit on top of it.
Second cousin
The first relationship where the range gets genuinely wide.
Half sibling
Indistinguishable from grandparent and aunt on cM alone.
Getting your raw data
23andMe raw data
What the download contains, what the columns mean, and what it is not.
AncestryDNA raw data
What the download contains, what the columns mean, and what it is not.
Finding a testing service
Match research library
Specific answers for the questions that appear after you receive a match result.
850 cM shared DNA: what could it mean?
A practical way to read an 850 cM DNA match, the relationships that commonly overlap there, and the evidence that narrows the list.
1,300 cM shared DNA: close, but still not conclusive
What a 1,300 cM DNA match can mean, why several close-family paths overlap, and how to check them without jumping to conclusions.
1,750 cM shared DNA: the close-family overlap zone
Why 1,750 cM often raises a half-sibling, aunt/uncle, or grandparent question—and what can actually separate those possibilities.
425 cM shared DNA: a useful clue with a wide family tree
How to approach a 425 cM DNA match using age, shared matches, and evidence instead of an overconfident relationship label.
212 cM shared DNA: close enough to investigate
A grounded way to interpret a 212 cM DNA match, assess relationship possibilities, and turn a number into a useful research lead.
90 cM shared DNA: useful, but not self-explanatory
What a 90 cM DNA match can tell you, how segment shape changes its meaning, and where to be cautious with distant-match conclusions.
700 cM shared DNA: could it be a first cousin?
How to assess a 700 cM match without mistaking a plausible first-cousin result for a certainty.
1,000 cM shared DNA: use a checklist, not a guess
A practical evidence checklist for interpreting a 1,000 cM DNA match among several close family possibilities.
1,500 cM shared DNA: several close relationships still fit
A careful guide to the relationship possibilities around 1,500 shared cM, including the evidence that distinguishes them.
200 cM shared DNA: turn a cousin-range result into a lead
How to use a 200 cM DNA match to build a cousin hypothesis, identify a shared-match cluster, and keep uncertainty visible.
400 cM shared DNA: is this a first cousin?
Why 400 cM can fit several cousin and half-family paths, and the evidence that makes a first-cousin hypothesis stronger or weaker.
Can relatives share no detectable DNA?
Why a real genealogical relationship can leave no detectable autosomal DNA, and when a zero-match result is meaningful.
What your longest DNA segment can tell you
How to interpret the longest shared DNA segment beside total cM, segment count, and family-tree evidence without turning one measurement into a relationship verdict.
Shared DNA matches: how to place a match on your family tree
A careful workflow for using shared DNA matches to identify a family branch while accounting for platform thresholds, endogamy, and incomplete trees.
Fully identical regions: a useful clue in sibling questions
What fully identical regions are, why full siblings often have them, and why this one clue still needs a family-tree explanation.
Centimorgans versus DNA percentage: two ways to describe sharing
Why cM and DNA percentages answer different questions, how conversions work, and why reported cM should remain the primary match measurement.
How DNA sites estimate relationship ranges
Why consumer DNA services can label the same match differently, what their estimates actually use, and how to turn a label into a responsible research question.