9) Tatiana Casiraghi (Age: 31; Net worth: $2.2 billion)

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Billionaire heiress Tatiana is a member of the Monaco’s royal family. She is married to Andrea Casiraghi, son of Caroline, Princess of Hanover. He is fourth in line to the throne.

Tatiana was rich even before her wedding. She is the granddaughter of brewery baron Mario Santo Domingo, who left one-sixth of his wealth to his granddaughter.