It could happen to anyone. You’re there having dinner at the home of your new boyfriend or girlfriend, getting on with their parents like a house on fire. Then suddenly.. What’s that sitting on the mantlepiece? An old family photograph with the beaming face of someon who’s a dead-ringer for your grandpa staring back at you.

And then it hits you. Your new girlfriend is actually your cousin. And you’ve already done the deed.

Well, okay, it probably wouldn’t happen to that many people, at least not in the good old US where the population is constantly rising with new babies being born, immigrants flooding in and kids flying the nest the minute they’re out of college. But it’s an altogether different story in lonely old Iceland, where its measly population of 320,000 or so souls share a long and common ancestry. Here, such confusing familial relations are far more common than most people would like.

With such a close-knit gene pool, it’s almost inevitable that people may end up sleeping with their relatives – first cousins, second cousins and so on, but it’s not a situation that the good Icelandic folk are happy about. If they could, they’d rather shy away from incestuous relations, thank you very much.

Now, there’s an app to help them avoid it.

News of Iceland reports that the app was built using data from an online genealogy database, Islendingabok, the Book of Icelanders, which stores detailed family information for the 720,000 or so people that’ve been born on Iceland since the Vikings first colonized it. The mobile version was built after a competition was launched by Iselandingabok’s founder Friorik Skulason, who offered a $9,000 pirze to whoever could build the best app.

However the winning design from Sad Engineer Studios, IslendingaApp SES, goes even further than the original website by adding a handy new feature called “bump”. As the name suggests, this lets two users bump their Android smartphones together and find out if there might be any potentially awkward family connections that ought to prevent them from getting too ‘close’. If the app thinks they might be just a little too familiar for their own good, it’ll sound an “incest alarm’ to discreetly warn each user.

Talking to the Digital Trends website, the developers had this to say:

“The incest prevention feature is a ‘fun’ feature that users can enable through the options menu, which notifies them with either text or sound if the person they bump together with is related to them”.

“We aren’t sure if other countries have such interestingly interwoven bloodlines like we do, but we’re pretty sure the Icelandic genealogy database is unique in its completeness.”

The developers say they can’t be sure if the app has been able to help anyone avoid getting into awkward situations yet. Nevertheless, IslendingaApp SES seems to have gone down well with Iceland’s single-folk so far – boasting a 4.6 out of 5 rating from 18 reviews so far.