The number of bill i onaires under the age of 40, according to the latest rankings. The world’s youngest billionaire i s Perenna Kei, 24, with an estimated net worth of $1.3bn ( R1 5 . 3 4bn). She oversees an 85% stake in Logan Property Holdings, which is headquartered in the southern Chinese cit y of Shenzhen, bordering Hong Kong, and develops real estate for the Chinese market. The company is run by her father, Ji Haipeng. The youngest new billionaires on the list are Evan Spiegel, 24, and Bobby Murphy, 25, who co-founded mobile messaging app Snapchat, and are each worth $1.5bn (R17.7bn), said.