Millions of American Irish, especially those in New York, may be directly descended from Niall of the Nine Hostages, the most prolific warrior in Irish history.

A team of geneticists at Trinity College Dublin led by Professor Dan Bradley recently discovered that as many as 3 million men and women worldwide may be descendents of the Irish warlord, who was  the Irish “High King” at Tara, the ancient center of Ireland from A.D. 379 to A.D. 405.

Harvard Prof. Henry Louis Gates Jr., who made headlines when he was arrested by an Irish police officer while trying to break into his own locked home, is also a descendent of Niall of the Nine Hostages — and is related to the cop who booked him!

The story of Niall of the Nine Hostages is already the stuff of legend, which has been passed on to countless Irish schoolchildren over the years.

The supposedly fearless leader battled the English, the Scots, the French and even the Romans, and struck fear into the heart of his enemies. His dynasty lasted for centuries, continuing up until the Elizabethan conquest of Ireland at the end of the 16th century.

Legend has it that it was Niall of the Nine Hostages who on a raid in Wales, captured a young slave, and brought him to Ireland. That slave would later escape, and go to become Ireland’s patron saint, St. Patrick.

But one story not told to most Irish elementary schoolchildren was Niall’s sexual prowess.

When it came to the bedroom, it seems that Niall of the Nine Hostages was even more fearless and energetic than he was on the battlefield.

This warlord was responsible for the very common Irish surname “O’Neill” (“Ui Neill” in Gaelic) – which literally means ‘descendant son of Niall' – also the name of Irish pubs all over the world.)

The researchers also found that as many as one in 12 men in Ireland have the same DNA as the Irish king – and in Ireland’s northwest, that figure rises to one in five.

"We sampled 60 people with these names and found the strongest association was with them,” Bradley told the London Independent. “Before this, everything was mythology, but now there does seem to have been a single male ancestor of this group of powerful dynasties."

"In many countries, powerful men historically have more children, and it's not that hard to believe that it happened in Ireland too.

"We estimate there are maybe two to three million descendants in the modern age, with a concentration in Ireland, obviously. Then there are Scotland and New York  - you find the particular chromosome in reasonable frequency in New Yorkers of European descent.”

That means that around one in 50 New Yorkers who have European roots – with surnames such as O'Connor, Flynn, Egan, Hynes, O'Reilly and Quinn– have the same genetic signature as Niall of the Nine Hostages, Bradley said.

Which prompted Peter Quinn, the renowned Irish-American author from the Bronx, to tell the New York Times, "I hope this means that I inherit a castle in Ireland."

So Niall joins Thomas Jefferson and Genghis Khan as one of the major historical figures when it comes to DNA.

Jefferson, the third president of the U.S., slept with one of his slaves, a woman called Sally Hemings, and fathered a child with her. A 1998 study found that Jefferson has an extremely rare DNA type, his Y chromosome belonging to just 1 percent of the population.

A 2003 study found that 8 percent of all Mongolian males are the descendents of Genghis Khan, sharing with him the same Y chromosome. His son had as many as 40 sons, and his grandson, as many as 22. The Khan family may have as many as 16 million descendants in Asia today.