Key Takeaways
- Big databases matter: More test-takers mean closer matches are likelier to show up.
- Centimorgans (cM) translate to closeness: Think of cM as the DNA “yardstick.” More shared cM usually signals a closer relative.
- Upload once, search everywhere: Export your raw file to GEDmatch and other portals so you don’t miss cousins who used a different company.
- Privacy sits in your hands: Most sites let you opt in or opt out of law-enforcement searches with a single toggle.
- Patience wins: No strong lead today? New kits arrive daily. Set alerts and check back each month.
DNA Relative Matching
It’s exciting, and a little scary, to open a match list for the first time. You’ll see numbers, acronyms, and strangers who might be family. Let’s slow down and translate the basics.
Your kit compares autosomal DNA, the 22 chromosome pairs you inherit from both parents. When two people share long, identical stretches, the software flags those pieces as identical by descent, evidence that you both got that DNA from a recent common ancestor.
Scientists measure each shared stretch in centimorgans (cM). A centimorgan is a unit of genetic distance, not a physical length. The higher the total cM between two kits, the closer the likely relationship.
| Likely Relationship | Typical Shared cM | How It Looks in the Results |
|---|---|---|
| Parent / Child | ~3,500 | Dozens of very long segments across many chromosomes |
| Grandparent | ~1,700 | Long segments on half the chromosomes |
| First Cousin | ~850 | Several segments over 50 cM |
| Second Cousin | ~230 | Mix of long and short pieces |
Why Database Size Counts
Imagine fishing with a net the size of a bathtub versus the size of a football field. AncestryDNA has more than twenty million profiles, so your “net” is huge. Smaller sites, though still valuable, may miss that one cousin who holds your missing surname.
If your goal is family-history research first, our guide to the best DNA tests for ancestry explains why AncestryDNA is usually the best starting kit. Uploading your raw data widens the net without buying a second kit.
Choose the Best Test
Picking a company can feel like betting on the right horse. Here’s a quick, no-jargon guide:
- AncestryDNA — Biggest match list, excellent family-tree tools. Lacks a chromosome browser.
- 23andMe — Adds health reports. Includes a browser to see exactly where segments overlap.
- MyHeritage — Smaller U.S. presence but strong in Europe and Latin America. Its “cM Explainer” guesses relationships for you.
- FamilyTreeDNA — Offers Y-DNA and mtDNA for deep paternal or maternal lines. Smaller autosomal pool.
- GEDmatch (upload) — A free, third-party site that lets kits from all brands compare in one place.
Reader tip: Buy one main kit, often Ancestry for its size, then upload the raw file to every free portal allowed. That single step can double your cousin list overnight.
Step-by-Step Search Plan
Searching without a map leads to overwhelm. Follow these four checkpoints.
1. Sort Your Matches
Start with the person who shares the most cM. If a known relative (say, Mom) also tested, label every cousin who overlaps with her as """Maternal.""" Most sites offer a Shared Matches button to speed this up.
2. Build a Mirror Tree
Open a blank family-tree program. For each top cousin, add their parents and grandparents using public obituaries, census pages, or social-media hints. You’ll soon spot repeat surnames or hometowns that point toward a common branch.
3. Triangulate Segments
Upload your best matches to GEDmatch and run the Triangulation tool. It highlights chromosome spots you share with two or more cousins at once. When that happens, all of you inherited that exact DNA block from the same ancestor, and your investigation narrows to one lineage.
4. Confirm With Records
Once a likely ancestor appears, chase birth certificates, marriage licenses, and newspaper clippings. A polite message, “Hi, I think we share Great-Grandpa James,” often unlocks family stories no database can hold.
Privacy and Feelings Matter
Finding family can be joyful and jarring in the same breath. It’s normal to feel anxious before clicking “View Matches.”
- Law-enforcement access: Most companies require your explicit opt-in before police can search your profile, and they still need a warrant. Check your settings.
- Unexpected parentage: Roughly one in fifty testers discovers that a parent or grandparent isn’t biologically related. If that possibility worries you, talk it through with a counselor first.
- Data deletion: All major kits let you wipe your DNA file and destroy the sample. Keep the power to reverse course.
Remember: DNA tells a genetic story, not the whole story. You decide how, when, and with whom to share each chapter.
Common Roadblocks—and Work—arounds
- Endogamy or cousin marriage: Groups with tight historical communities, such as Acadians and Ashkenazi Jews, share extra DNA. Focus on segments longer than 15 cM and ignore the tiny ones that create noise.
- Small databases for your heritage: If you have recent African or Asian roots, matches may be sparse. Upload to sites with stronger coverage in those regions and invite relatives to test.
- No close matches yet: Databases grow daily. Set email alerts for new high-cM hits and re-check monthly. Even a distant third cousin can break a case once fresh records appear online.
Next Steps
- Order a kit that aligns with your budget and region of interest. Watch for holiday sales.
- Plan your uploads — save the raw file once results arrive.
- Set emotional expectations with loved ones before sharing discoveries.
- Find community — forums like DNAAdoption or SearchAngels pair newcomers with seasoned volunteers.
Finding family is rarely instant, but each clue builds on the last. With steady work—plus empathy for yourself and others—you can turn cold paperwork into warm connections.
The Best DNA Test to Find Lost Relatives
1. 23andMe - Our Top Pick
23andMe DNA Test Cons
- No cross-platform support — You can’t upload raw genetic data from competitors.
23andMe does all three tests: mtDNA, Y-DNA, and autosomal. Combined with a massive DNA database, it ranks among the most accurate options for ancestry.
Here’s our 23andMe review if you want to learn more.
2. AncestryDNA
Ancestry DNA Test Cons
- Limited access — To build a family tree, you must pay monthly fees to access public records and other users’ family trees.
- Doesn’t estimate your racial group —AncestryDNA only performs genetic matches based on geography, not racial profile (e.g., Asian, American, and European).
Additional services can get expensive. However, its massive database has made it a highly trusted DNA test, so many think it earns its price tag. You can learn more about AncestryDNA here.
