(CNN) -- The path that brought U.S. citizen David Coleman Headley to the point of pleading guilty to involvement in two international terrorism plots is complicated and twisted.



His life, in many ways, is far from the average American experience, but he's also very much a product of a typical American upbringing.



He's an unusual fusion, a product of two worlds, a rare blending of East and West. And because of his unusual background, Headley, experts say, is one of the most unusual and important American-born terrorists.



Even his eyes -- one blue and one brown -- reflect the double life he has lived almost since the day he was born.



Headley pleaded guilty Thursday to all 12 charges against him in connection with the four-day siege on India's financial capital in 2008 that left more than 160 people dead and a planned attack in Denmark.



Headley, the son of an American mother and Pakistani father, was accused of extensive involvement in planning the devastating attacks on hotels in Mumbai, which the Indian government says were carried out by the Pakistan-based terrorist group Lashkar-e-Tayyiba. At least six Americans were among the dead.



Headley, 49, was indicted last October and charged by the U.S. government for conspiracy to murder and maim people in India and provide material support to a foreign terrorist organization.



He initially pleaded not guilty to the charges, but he has changed his plea as part of a deal with the government to cooperate with investigators and possibly to avoid the death penalty he might have received if convicted on some of the charges.



In the federal courtroom in Chicago, Illinois, on Thursday, Headley told the judge that he did not dispute any of the 12 charges. By pleading guilty, he also gave up his right to appeal in the case.



He faced six counts of conspiracy to bomb locations in India and to murder and maim persons in India and Denmark, and six counts of aiding and abetting the murder of U.S. citizens in India.



The indictment against him charged that Headley scouted targets in Mumbai for more than two years to set up the November 2008 attacks. He was also accused of planning a terrorist attack on a Danish newspaper, which was never carried out. The newspaper became the target of Muslim fury in 2005 after it published cartoons depicting the Prophet Muhammad in a manner offensive to Muslims.



Even family asks: Who is David Coleman Headley?



Now that he's admitted to conspiracy to murder and maim in the Mumbai attack, even members of his own family are wondering who David Headley really is.



"I was really shocked. And just didn't expect something like that. And I mean such a hands-on accusation," said William Headley, his uncle, reflecting on when he first learned of the government's accusations against his nephew. "It was like you had poured cold water inside my chest."



David Coleman Headley was born in 1960 in Washington, D.C., but with a different name: at birth, he was given the Urdu name Daood Gilani.



He was the son of an eccentric, flamboyant and rebellious high society mother from Philadelphia, Pennsylvania, Serrill Headley; and a strict, formal Pakistani diplomat father, Sayed Salim Gilani. The couple met at the Pakistani Embassy in Washington but moved to Lahore, Pakistan, when their son was very young.



"He was the first baby I had anything to do with," his uncle William Headley said. "He was the first baby I ever touched or held or anything like that. And somewhere I have a photograph of me in my pajamas holding little Daood. ... He was a nice-looking little baby."



Fractious union of East and West



After only a few years, Daood's parents split up, an early sign of the fractious union of East and West.



The separation left Daood straddled between his traditional Muslim father and his very Western, very American mother. For a time, his mother remained in Pakistan, but she eventually returned to Philadelphia, where she opened a popular bar called the Khyber
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