A family history website has launched a new service to help track down people's unknown relatives using DNA tests.
DNA testing will be used to identify family connections
Ancestry.co.uk says it can help people identify living genetic cousins and learn about the ethnic roots of their distant ancestors.
Subscribers will have a swab taken from inside their cheek for cells to be kept on a database anonymously. If a match is found, both people will be informed.
Those using the service will pay between £74 and £99 for a DNA test kit.
If a match is found, both people will automatically receive a message.
But the site said it would reveal only if people were related, and not how, leaving genealogists the "exciting challenge" of discovering the precise nature of the connection.
Users will be able to create special "DNA groups" for people with the same surname, in a similar manner to how social networking websites operate.
Megan Smolenyak, Ancestry's chief family historian, said: "DNA testing in family history is reaching a critical mass.
"As more people add their results, Ancestry's DNA database will become a powerful asset for users to make connections and discover their family tree."
The website, which says it has about 15 million registered users, is offering three different DNA tests.
A paternal lineage test, analysing the Y-chromosome DNA which is passed virtually unchanged between father and son, costs £74.
This test, which is not available to women because they lack a Y-chromosome, is able to confirm a shared ancestor in past generations.
However, for £99 users of the site can get a more comprehensive version of the same test.
And users can undergo a maternal lineage test, for £89, which looks at the mitochondrial DNA passed from mother to child.
Simon Harper, Ancestry's managing director, said: "What [users] will be able to do is find out about their own ancestral DNA and then we may well show them a person in Australia or Canada who has a similar DNA match and that match may go back a number of generations to a common ancestor."
He added: "Given the sheer size of Ancestry's online family history community, the potential of DNA to help our users discover new relatives and learn more about their family's history is enormous."