Youngest billionaires: How did they make their money?

Four of the world's youngest billionaires turned high-tech startups into massive fortunes and earned spots on Forbes 2017 list of billionaires.

John Collison, 26, and his brother Patrick Collison, 28, co-founded Stripe, a software platform for mobile device e-commerce payments. The Irish siblings are each worth $1.1 billion. Worth $4 billion each are Evan Spiegel, 26, and Bobby Murphy, 28, who together built Snapchat.

After Snap’s March 2 initial public offering, Spiegel and Murphy became the only two billionaires under the age of 30 currently running a publicly-traded company.

The two sets of co-founders from are among 23 of the ultra-high echelon earners under the age of 40 who made their money in the tech industry, according the financial magazine that identifies more than 2,000 billionaires worldwide of all ages.

For the second year in a row, 20-year-old Alexandra Andresen of Norway is the world’s youngest billionaire, according to list published this week by Forbes for the 30th year. She and her sister Katharina Andresen, 21, first appeared on the list in 2016 after their father gave them control of the family investment company. Their wealth is listed at $1.2 billion each.

Here are the 11 billionaires age 30 and younger with the youngest listed first:

1678. Alexandra Andresen, 20, 1.2 billion, investments (Norway)

1678. Katharina Andresen, 21, $1.2 billion, investments (Norway)

1290. Gustav Magnar Witzoe, 23, $1.6 billion, fish farming (Norway)

441. Evan Spiegel, $4 billion, 26, Snapchat (United States)

1795. John Collison, $1.1 billion, 26, Stripe (Ireland)

1795. Ludwig Theodor Braun, $1.1 billion, 27, medical technology (Germany)

441. Bobby Murphy, $4 billion, 28, Snapchat (United States)

1795. Patrick Collison, $1.1 billion, 28, Stripe (Ireland)

1567. Wang Han, $1.3 billion, 29, airline (China)

116. Lukas Walton, $11.3 billion, 30, Walmart (United States)

1567. Eva Maria Braun-Luedicke, 30, $1.3 billion, medical technology (Germany)