The age range of people on the 2025 Forbes World's Billionaires list spans the better part of a century. Youngest is 19-year-old Johannes von Baumbach, an heir to the Boehringer Ingelheim fortune, a company best known as the largest private pharmaceutical company.
The oldest, at 103, is George Joseph, the founder of in 1962 of Mercury General, an insurance provider with $5.5 billion in annual revenues.
The World’s Billionaires list is a ranking of every person who, in Forbes’ estimation, had a net worth of $1 billion or more as of March 7, 2025. To identify them, Forbes researchers tried to meet with billionaires in person or speak with them virtually or by phone. They also interviewed their employees, handlers, asset managers and financial advisors, rivals, peers and attorneys.
They also pored over thousands of documents from the Securities and Exchange Commission and other regulators, along with court filings, probate records and news articles. They took into account all types of assets, and factored in known debt and charitable giving.
Researchers excluded dispersed family fortunes, though they listed wealth belonging to the immediate family of the living founder of a fortune under the founder’s name. In some cases, they also included wealth held by the immediate family member of an heir.
See the gallery for the 15 youngest American billionaires on the Forbes list.
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