This page explains points to watch out for when researching your ancestors.

“It’s a hanging wisteria crest, so we must be Fujiwara” → No, a family crest alone cannot trace your ancestors

Beginners tend to jump to conclusions such as “It’s a hanging wisteria (sagari-fuji) crest, so we are Fujiwara!”, and
many books are published as if family crests could tell you who your ancestors were,
but basically you cannot trace your ancestors from a family crest alone.

The whole family does not necessarily use the same one. Crests are often changed when a branch family is founded, on a celebration, to commemorate or pray for something, when given by a superior, when the crest handed down through the generations is unknown and someone picks a design they like, or out of a wish to be associated with someone. Just as with a keizu that records a clan name that is not true (不実本姓), a family might also adopt a wisteria crest for political reasons, such as wanting to belong to a powerful clan (for example the Fujiwara or the Minamoto), or wanting people to think they are Fujiwara when they are not. However rare the design, someone a few generations back may have used it as a model for their own crest, or it may be a coincidence.

Conversely, there are Fujiwara lines whose crest is not a wisteria at all.

Books claiming that you can learn your ancestors from your crest are sold because such content seems easy and appeals to readers. Do not easily believe it either when someone who looks like an expert said so on a television program. Check it yourself, for example by consulting specialist books.

For now, absolutely stop making easy assumptions such as “it’s a Genji-guruma or a sasa-rindō, so we are Genji.” If you research several family lines of your own ancestors, you should come to see this within a few years.

In reality

Except for some crests such as the chrysanthemum and the hollyhock (kiku and aoi), family crests could be adopted and changed relatively freely.

There seem to have been cases where a crest was handed over by a superior or subordinate, and, as with a keizu that records a clan name that is not true, cases where the crest of a prestigious clan was adopted as one’s own to disguise the authority of one’s family. In the end, unless you establish the paternal line of descent, it is not clear which clan your hon-sei (本姓, clan name) is.

Also, even if the crest is the same, unrelated families may use the same crest, so they are not necessarily of the same kin. In theory the same design can appear by coincidence, and a design that was handed over, used as a model or became fashionable may be used by entirely separate families.

Even with the same surname (myōji), before the Edo period there seem to have been cases where someone who moved into a vacant house used the name and the crest, so you cannot conclude that people with the same surname living nearby are of the same kin. In the end, you need to make the keizu clear.

“He’s called Tarō, so he must be the eldest son” → No, not necessarily

Do you assume that “if the brothers’ names are Tarō, Jirō and Saburō, they must be the eldest, second and third sons”?

If that were so, it would feel neat.
But that is not necessarily the case.

In fact, our director’s ancestors include the following cases:

All three brothers were named “○-tarō”
All three brothers were named “○-jirō”
The eldest son was named “○-gorō” and the fifth son “Koichi (小一)”

In cases like these, especially the third, you could end up understanding the brothers’ order the wrong way around. Please check carefully.

“He died first, so he must be the parent” → No, children sometimes die young

It is a general tendency for parents to die before their children, but everyone knows that the reverse also happens. With ancestors whose faces you have never seen, however, it is easy to get this wrong by mistake, so take care.

In one prefectural history, the parent-child relationship of our director’s ancestors is written the wrong way around. Probably the author misunderstood because the son and his wife died before the parents did. We do not know the cause of death, but it is possible that younger people died from an epidemic or the like.

The relationship is written in the removed family registers, on gravestones and in old documents, so the statement in the prefectural history is a factual error in the record (jijitsu-gonin kisai, 事実誤認記載). Even historians make factual errors like this, so please be careful.

“This surname seems to be Fujiwara” “Our family is of the Seiwa Genji line” → No, you need to check whether the paternal line of descent connects

Surname dictionaries and websites featuring surnames say things like “the surname ‘○○’ is Seiwa Genji.”

However, the hon-sei (本姓, clan name) or clan, such as Fujiwara, Minamoto (Genji) and Taira (Heishi), is about the paternal line of descent, so you cannot tell which clan you belong to unless you trace your ancestors along the paternal line of descent.

What a surname dictionary states is which clan the first person to bear that surname belonged to. Even if the first generation was Kanmu Heishi, if the second generation was an adopted son-in-law (mukoyōshi) from the Tachibana clan, then from the second generation until the next adopted son-in-law, the family is Tachibana.

Moreover, there are many families that use the same surname with entirely different origins. You can see this from the fact that most surnames are given several clan names of origin.

So do not casually assume, “It was written in a surname dictionary, so we are Fujiwara.” Trace your ancestors along the paternal line of descent and check.

In reality

Genji, Heishi, Fujiwara and so on are called hon-sei (本姓), and a hon-sei is the name of a paternal line of descent. A surname (myōji, 苗字 or 名字), on the other hand, is a family name (kamei, 家名).

When an adopted son-in-law has entered the family, the paternal line of descent of the head of the family changes, and the hon-sei may have become that of the adopted son-in-law himself. A hon-sei follows the paternal line of descent, so in principle it does not change unless a new family name is bestowed by the Emperor (shisei), whereas a surname changes through marrying into a family, changing the name one uses, and so on.

Therefore, even if the first generation of the ○○ family was Seiwa Genji, if the second generation was an adopted son-in-law from the Fujiwara, the hon-sei from the second generation on is Fujiwara. At most, all you can say is that the first generation may have been Seiwa Genji.

Furthermore, it is well known that, because lineage was important in the past, quite a few families made a keizu that records a clan name that is not true. For this reason, even for the first generation, you cannot be sure it was Seiwa Genji unless you carefully confirm the paternal line of descent. Do not swallow family traditions whole. Treat “Seiwa Genji” as a hint, and above all verify it by tracing the paternal line of descent.

As for this, there were already cases by the Sengoku period of being adopted for political reasons and changing one’s hon-sei without a bestowal of a family name, and by around the Edo period the two seem to have been thoroughly confused.

For the reasons above and others, there are many cases where surnames have different places of origin because each family took the name of a place of the same name in different regions, and in addition there are cases where people changed to a name they liked under the Meiji-period decree requiring everyone to use a surname (myōji hishō-rei). So even if a surname dictionary states that a surname is Kanmu Heishi, you cannot know whether your own hon-sei is really Kanmu Heishi. You must trace the paternal line of descent and also trace the origin of the surname.

“Our ancestors carried a sword, so they were samurai”

This is a misunderstanding caused by mistakes in history education. Commoners could also carry a wakizashi (a short sword of about 60 cm or less).

“There was no freedom of movement in the Edo period, so they must have lived in the same place all along”

This is a misunderstanding caused by mistakes in history education. In fact, there was quite a lot of seasonal migrant work, travel and moving house.

“Commoners in the Edo period had no surnames” “After the Meiji period they called themselves whatever they liked, or the lord gave them one”

This is a misunderstanding caused by mistakes in history education. They were simply not allowed to use them officially (in administrative procedures and the like). Many commoner families passed surnames down and used them privately as self-chosen names.

There may be families who were given a surname by their lord, but think realistically. Would a lord give one to every one of his subjects just because they were his subjects? That sounds like an urban legend.

The reason many people in a district share the same surname is probably that they are the main and branch families of the same kin.