The 2026 Forbes 400 includes 10 billionaires under 40 for the first time, up from four in 2025, with AI accounting for all seven newcomers. Four are Anthropic cofounders, each valued at an estimated $15.5 billion, while OpenAI cofounder Greg Brockman leads the new under-40 entrants with $25.5 billion. The youngest members are Anduril founder Palmer Luckey, worth $5.9 billion, and Cognition co-founder Steven Hao, worth an estimated fortune linked to the company’s $2 billion funding round at a $48 billion valuation. The three returnees are Edwin Chen, Vlad Tenev and Lukas Walton, who is the group’s richest member at $44.4 billion and the only heir. Collectively, the 10 are worth $169 billion, down from $357 billion in 2025, largely because Mark Zuckerberg aged out of the group. The broader Forbes 400 reached a combined $8 trillion, while the admission threshold rose to $4.4 billion. Anthropic and OpenAI have submitted confidential IPO filings, and Anthropic has selected Nasdaq for a planned October debut. Anthropic also exceeded OpenAI’s quarterly revenue in the second quarter, reporting $11.6 billion versus $6.7 billion, according to CNBC and The Wall Street Journal.