If you are preparing to go exploring in your family tree, beware of fallen branches.
A study has shown that amateur genealogists, hoping to find an aristocratic or celebrity connection, often trip over something painful.
Around one in five who research their ancestors on the internet find illegitimate children.
Seven per cent apparently discover a convicted criminal in their clan, and 14 per cent come across someone who has forsaken the family name for some reason.
Six per cent discover secret adoptions or that their parents or grandparents were unwed.
The findings are from genealogy website Ancestry.co.uk.
Its survey found that more than one in three adults have conducted research of this type online in the past decade, and an estimated 1.4million have made contact with newly discovered family members.
The hobby is becoming increasingly popular – and much easier – as more records are placed online.
Registers of births, marriages and deaths, as well as census information and emigration records are now readily available.
The site’s managing director, Simon Harper, said: “This research confirms that for most Britons, the odds are that somewhere in their family’s past there is a secret just waiting to be discovered.”
Many of these discoveries are exciting ones.
The survey found that 23 per cent confirm links to the aristocracy, famous historical figures or rich landowners.
And four per cent claim to have found connections to royal blood.
But there is always the chance of turning up a bad apple – as several high-profile figures have recently discovered.
Actor Stephen Fry learnt that his great-great uncle Ernest Pring was an inmate of Knutsford prison in Cheshire in 1893, and his wife was committed to a workhouse.
Similarly, fellow television presenter Griff Rhys Jones learnt that far from dying in a Victorian train crash as he had always believed, his greatgrandfather Daniel Price died after cracking his head during a drunken fight outside a pub in Llanelli in 1897.
Both found out the truth through BBC series Who Do You Think You Are?, whose latest subject, actor John Hurt, revealed that his cherished Irish ancestry turned out to be a family myth and that his forefathers hailed from Croydon.
Mr Harper said: “With billions of historical records now available online, the internet has made it possible for us all to put our family’s tall tales to the test.
“It can also put speculation and rumours passed down through generations to rest and can even bring members together for the first time.”
He added: “Exploring family history can be very emotional as we start to comprehend how difficult the lives of our ancestors often were.
“Yet discovering more about them, their successes failures and choices, also helps us to appreciate them as people – even if we never knew them personally – and in doing so their contribution to our own lives.”