Six Generations, One Page: How to Read a Japanese Family Tree
A completed Japanese family tree, built from koseki records, often surprises people who were expecting something closer to a Western pedigree chart. The conventions are different, and a few of those differences are worth knowing before the document lands in your inbox.
Names change more than expected
A single ancestor can appear under more than one name across their life — a birth name, a name adopted through marriage into a family with no male heir (mukoyōshi), or a name changed through formal adoption. This isn't a research error. It's an accurate reflection of how names worked under the koseki system, where marriage and adoption could genuinely change a person's registered family name.
Adoption is common, and it's not hidden
Adoption — of children, but also, distinctively, of adult sons-in-law to continue a family line — appears throughout Japanese family trees far more often than in most Western family history. A tree with several adoptions across generations isn't unusual or a sign of anything remarkable. It reflects a common legal and cultural mechanism for keeping a household name and line active.
Dates follow Japanese era names
Traditional records date events by era name and year (e.g., Meiji 22, not 1889) rather than the Western calendar. A well-prepared family tree converts these to Western dates for clarity, but it's useful to know why an original document might show "明治22年" instead of a number you recognize.
The structure reads top-to-bottom by generation, not left-to-right by branch
Where a Western pedigree chart typically fans outward from one person, a Japanese-style family tree is often organized by generation, moving down the page, with siblings and their descendants grouped horizontally within each generation. Once you know to read it that way, following a specific line down through the generations becomes straightforward.
What to do if something looks wrong
If a name, date, or relationship seems inconsistent with what your family always understood, it's worth asking rather than assuming an error. Sometimes family oral history and legal koseki records genuinely diverge — an unofficial adoption never formally registered, a relationship the family described differently than the legal record shows. Both versions can be true in their own way, and a good researcher will walk through the discrepancy with you rather than just handing over a document and moving on.
TADOROOTS delivers every family tree with a summary report explaining exactly how to read it, and time to ask questions about anything that doesn't match what you expected.
Reading the era names
Japan's era name (gengō) system assigns a name to each emperor's reign, and years are counted from its start: Meiji (1868–1912), Taishō (1912–1926), Shōwa (1926–1989), Heisei (1989–2019), and Reiwa (2019–present). A koseki entry dated "明治22年" refers to the 22nd year of the Meiji era, which converts to 1889. Most family trees prepared for overseas clients convert every date to the Western calendar, but original source documents will still show era dates, so recognizing the pattern helps when reviewing scanned records alongside the finished tree.
Frequently asked questions
Why do some relatives on the tree have no birth date listed? Older koseki entries sometimes recorded only a death or marriage date if the birth predated reliable record-keeping in that municipality, or if the original entry was damaged or illegible. A missing date is noted as such rather than guessed.
Can the family tree be updated later if new information comes to light? Yes. Family trees aren't static documents — if a Roots Tour, further archive research, or a newly located relative adds information, the tree can be revised to reflect it.