No. 4: Scott Duncan

Forbes.com: Youngest Billionaires in the World

Age: 29
Net Worth: $4.1 billion

Scott Duncan is one of four children of the late energy pipeline entrepreneur Dan Duncan, the former richest man in Houston, who died in 2010 at age 77. Scott added $1 billion to his fortune in the last year as the company's share price climbed by one-fourth.

(Photo: Forbes.com)

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No. 10: Robert P... Age: 34
Net Worth: $1.5 billion
Apple hardware engineer turned wireless networking entrepreneur struck out on his own in 2005 with the goal of bringing affordable internet access to the world's emerging markets. Six years later, Pera became a billionaire when his Ubiquiti Networks went public in October 2011.

(Photo: Ubiquiti Networks)

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The opinions expressed are solely those of the author and do not necessarily reflect the views of Comcast.
No. 9: Ayman Har... Age: 33
Net Worth: $1.3 billion
Ayman Hariri is the second-youngest son of slain Lebanese Prime Minister Rafik Hariri, who left behind a fortune now shared by his five children. On the board of Saudi Oger, he has overseen mega construction projects such as the Princess Noura Bint Abdulrahman University for Women, and the King Abdullah Financial District, both in Saudi Arabia.

(Photo: Balcas Press/Abaca/Newscom)

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The opinions expressed are solely those of the author and do not necessarily reflect the views of Comcast.
No. 8: Sean Park... Age: 32
Net Worth: $2.1 billion
Facebook's first president is looking to disrupt the Web once again with Airtime, the social video site he plans to launch with his Napster co-founder, Shawn Fanning, by the end of 2012. He's also looking to fix the very music industry he helped break with Napster as an investor and board member of Swedish music platform, Spotify.

(Photo: Simon Dawson/Bloomberg via Getty Images)

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The opinions expressed are solely those of the author and do not necessarily reflect the views of Comcast.
No. 7: Fahd Hari... Age: 31
Net Worth: $1.3 billion
Fahd Hariri is the youngest son of slain Lebanese Prime Minister Rafic Hariri. He lives in Paris, where he got a degree in architecture. While still a student, he opened an interior design studio on the outskirts of the city, and sold furniture to clients in Saudi Arabia.

(Photo: Thomas Sampson/APP/Getty Images)

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The opinions expressed are solely those of the author and do not necessarily reflect the views of Comcast.
No. 6: Yang Huiy... Age: 30
Net Worth: $4.7 billion
Her low-key dad, Yeung Kwok Keung, transferred his holding of the family's main fortune, shares in family-controlled real estate developer Country Garden Holdings to her ahead of the company's Hong Kong IPO in 2007. Yang, China's richest person in 2007 (net worth then: $16.2 billion), has seen her fortune drop dramatically since, though she's wealthier than last year.

(Photo: Forbes.com)

More From Forbes:
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The opinions expressed are solely those of the author and do not necessarily reflect the views of Comcast.
No. 5: Eduardo S... Age: 30
Net Worth: $2 billion
Eduardo Saverin was immortalized in the movie, The "Social Network," which portrayed him being betrayed by his onetime best friend Mark Zuckerberg. The former pals started Facebook together at Harvard, with Brazilian-born Saverin apparently providing early seed money.

(Photo: Jason Kempin/Getty Images for Common Sense Media)

More From Forbes:
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The opinions expressed are solely those of the author and do not necessarily reflect the views of Comcast.
No. 4: Scott Dun... Age: 29
Net Worth: $4.1 billion
Scott Duncan is one of four children of the late energy pipeline entrepreneur Dan Duncan, the former richest man in Houston, who died in 2010 at age 77. Scott added $1 billion to his fortune in the last year as the company's share price climbed by one-fourth.

(Photo: Forbes.com)

More From Forbes:
The World’s Billionaires
The World’s Billionaire Newcomers
The World’s Billionaire Dropoffs
The Oldest Billionaires in the World

The opinions expressed are solely those of the author and do not necessarily reflect the views of Comcast.
No. 3: Albert Vo... Age: 28
Net Worth: $1.5 billion
Albert von Thurn und Taxis first joined Forbes' billionaire ranks at age 8 but officially inherited his fortune in 2001 on his 18th birthday. The eligible bachelor still lives in his family castle and races in a German auto-racing league.

(Photo: sportfotodienst/Newscom)

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The World’s Billionaires
The World’s Billionaire Newcomers
The World’s Billionaire Dropoffs
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The opinions expressed are solely those of the author and do not necessarily reflect the views of Comcast.
No. 2: Mark Zuck... Age: 27
Net Worth: $17.5 billion
Don't let the hoodie and the sandals fool you, the Facebook founder controls 56.9 percent of firm's total pre-IPO voting power. The company's IPO is expected to hit in the next few months, possibly boosting his net worth even higher. Zuckerberg is only 8 days older than former roommate Dustin Moskovitz.

(Photo: Justin Sullivan/Getty Images)

More From Forbes:
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The opinions expressed are solely those of the author and do not necessarily reflect the views of Comcast.
No. 1: Dustin Mo... Age: 27
Net Worth: $3.5 billion
Dustin Moskovitz was Mark Zuckerberg's Harvard roommate and Facebook's third employee. Despite his billions, he still bikes to work and flies commercial. Moskovitz has also joined Bill Gates' Giving Pledge. He is just 8 days younger than his friend.

(Photo: Agama)

More From Forbes:
The World’s Billionaires
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The World’s Billionaire Dropoffs
The Oldest Billionaires in the World

The opinions expressed are solely those of the author and do not necessarily reflect the views of Comcast.
More from Forbes... Click here to see the rest of Forbes' list of the world's youngest billionaires.