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Heirs and Heiresses of the Wealthiest People in America
fIn this handout photo provided by Mayor Bloomberg's Press Office, the maid of honor Georgina Bloomberg, left, Mayor Michael Bloomberg and the bride Emma Bloomberg, right, pose for a photo before the ceremony. Emma Bloomberg was married on Saturday in a civil ceremony at the mayor's 26-acre country home in Westchester County. · Yahoo Finance · AP Photo

American parents are some of the most generous givers in the world, planning to leave an average of $175,000 to their children after they retire, according to a new study by HSBC. One out of every five inheritances will be worth more than $390,000.

Coming into that kind of money without having to work for it is nothing to sniff at — but what if you were born into billions?

America is home to the most billionaires in the world — 442 at last count. We decided to take a look at some of the richest American families and turn the spotlight from the billionaires themselves to the heirs and heiresses who are expected to live up to their family fortune.

The Koch Brothers

It’s hard to look at the Koch brothers as simply heirs to their late father’s multibillion-dollar fortune. Charles (left), 78, and David, 74, are worth an estimated $36 billion, making them the richest brothers in the U.S., but they’ve had a hand in the family business for decades. Today, each shares executive roles at Koch Industries, a global conglomerate and the second-largest privately-held company in the U.S., whose subsidiaries are involved in a range of industries, including refining, energy, and building products.

Zachary and Alexa Dell

Their father, Michael Dell, made his fortune founding the largest PC company in the U.S., Dell. Worth $15.9 billion, he’s the 25th richest person in the country.

Alexa Dell, 18, made headlines when she posted a slew of Instagram photos and tweets that revealed her family’s secret vacation spot to the public last year — undoing countless hours of work by their $2.7 million-a-year personal security team to keep their whereabouts private (they were on the family jet on their way to Fiji). Younger brother Zachary is already getting in the entrepreneurial spirit. At age 15, he co-owns a children’s sports camp in Dallas.

Brett Icahn

Brett’s father, Carl Icahn, 77, is the activist investor and founder of Icahn Enterprises and the 18th richest person in the U.S.

Brett, 40, may stand to inherit his father’s fortune, but the hedge fund manager is doing a decent job filling Dad’s shoes already. Carl Icahn threw Brett and his investment management partner, David Schechter, a multibillion-dollar bone in 2012, giving the pair free reign over $3 billion worth of capital from Icahn Enterprises. The move was something of a test, letting the junior Icahn prove his savvy as a hedge fund manager with the hopes of one day launching his own fund. Brett, who joined the family business as an investment analyst more than a decade ago, has produced returns as high as 96% in his new role.