18) Marie Besnier Beauvalot (Age: 34; Net worth: $2.5 billion)

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Marie inherited French dairy behemoth Lactalis along with her siblings. Together they own 100 percent of the company which their grandfather founded in the 1930s. They are working towards expanding the company internationally. Lactalis produces popular President brie.

17) Joe Gebbia (Age: 33; Net worth: $1.9 billion)

Joe is the co-founder and chief product officer of Airbnb, a peer-to-peer home and apartment rental company which has served 30 million guests since its inception. He came up with the idea with co-founder Brian Chesky in 2008 after graduating from the Rhode Island School of Design. He owns around 15 percent of the company.