Are people with the same surname related?

You meet someone with your surname and the question comes up: "Could we be family?" Sometimes, yes. Often, no. The surname alone does not settle it. This post explains why, and then what can settle it.

Why the same surname arose many times

Surnames were not handed out from a single list. They were formed from ordinary words, from place names and from given names. According to the Institute of the Polish Language of the Polish Academy of Sciences (IJP PAN), those three groups are the largest today. When bynames became hereditary surnames is covered in the blog's first post.

In the description of its surname dictionary, IJP PAN writes that identically sounding surnames often arose at different times and for different reasons. One example is Krupnik: in Old Polish a krupnik was a craftsman who made groats, later a groat soup, and later still a drink made from honey and roots. A surname can also have two possible sources. Lenartowski may come from the place name Lenartowice, or from the surname Lenart.

If one surname could arise for several reasons, it could also arise in several families with nothing to do with each other. Two people with the same surname may descend from two different first bearers. How surnames were built is the subject of our post on the endings -ski, -wicz and -ak.

Common and rare surnames

It seems likely that a rare surname makes a shared ancestor more probable. Research agrees, with caveats.

The geneticists Turi King and Mark Jobling of the University of Leicester compared the Y chromosomes of almost 1,700 men bearing one of 40 British surnames. The Y chromosome passes from father to son, as most hereditary surnames do. Shared ancestry within a surname generally grew stronger the rarer the surname was. On average 62% of the men fell into groups of shared descent, but depending on the surname the figure ranged from 0 to 87%. The authors also note earlier observations that surnames from common occupations and given names seem more likely to have had several founders than those from the names of small villages.

In the same paper, data on Irish surnames showed no such link with frequency. The authors put this down to the different population histories of Ireland and Britain. So these figures are about Britain, and we do not carry them over to Poland. The general lesson: a rare surname makes a shared ancestor more likely, but does not guarantee one. A common surname says almost nothing about it.

You can see how rare your surname is on Name Atlas, in the chapter "How rare is this surname?". It is a figure from the PESEL list, not a measure of kinship.

Place is a hint, not proof

If two families with the same surname live in the same area, that is a good lead. But only a lead.

The map in the chapter "Where is it most often registered?" shows the voivodeships where the surname's bearers have their permanent registered residence today. On the surname page we say plainly that this is an address in the register, not an actual address, and not information about a family's roots. People moved, and voivodeship borders changed. A voivodeship missing from the map is not zero either, because the PESEL list leaves out single occurrences.

The same goes for old records. Two men with the same surname in one parish may have been brothers, cousins or strangers. A shared place tells you where to look, not what you will find there. Our step-by-step guide shows how to read a surname page chapter by chapter.

What can confirm kinship

Documents

Kinship is confirmed by records of birth, marriage and death, from parish registers or civil registration. For each record, compare the parents' given names, the mother's maiden name, the parish and the dates. Geneteka shows both parents' given names and the mother's surname in its index, so you can often check this without ordering a scan. Our post on finding your ancestors goes from the papers at home to a record a hundred years old.

A family tree

Two people are related if their trees, built from records, meet in the same person. It is not enough for the same surname to appear in both trees. You have to reach one record: the same baptism, the same marriage, the same parents. If one tree ends in Lesser Poland in the 19th century and the other in Podlasie, a shared surname does not yet join them.

DNA

DNA can confirm what the records do not show, but each test sees something different.

• A Y-DNA test looks at the male line: a man's father, his father's father and so on back. That is how Susan C. Meates of the Guild of One-Name Studies, a society of researchers who study single surnames, describes it. The Y chromosome passes from father to son, typically unchanged, and in most cultures the surname follows the same path. Two men related in that line should match exactly or closely. A woman has no Y chromosome, so she needs a man from the line she is researching to take the test. Surname DNA projects build on this. Meates describes how they combine many bearers' tests with research in the records to find out which family trees with the surname are related and which are not.
• The link between surname and Y chromosome can break. Meates lists a name change, adoption, infidelity, and a child born outside marriage who took the mother's surname. Two men with the same surname may then have different results even though the records make them relatives.
• An autosomal test covers every branch of the tree, but usually reaches about five generations back, sometimes more. The geneticists Peter Ralph and Graham Coop write that second cousins share about 1/32 of their genome, and that people whose shared ancestor lived more than eight generations ago usually have not inherited any genetic material in common from that ancestor.

So finding no shared DNA in an autosomal test does not rule out distant kinship. And a Y-DNA match says that two male lines share an ancestor, but not who that ancestor was. The records show that. How an ancestor in your tree differs from an ancestor you carry DNA from is covered in our post on the history of genealogy.

What Name Atlas shows

Name Atlas is about the surname, not the family. A surname's page shows how many people bear it, how rare it is, where its bearers are registered and what it may mean. In the chapter on well-known people we say it plainly: "Sharing a surname does not mean being related." On the page that compares two surnames we add that a shared or similar surname does not mean a shared family, shared roots or shared nationality. What else a surname can and cannot tell you is gathered in our post on what a surname tells.

Look up your surname on Name Atlas.