Kei Perenna Hoi Ting of China has become the world's youngest billionaire, replacing Facebook co-founder Dustin Moskovitz, according to state-run China News Service. Hailing from Hong Kong, the 24-year-old woman holds an 85% stake, worth $1.3 billion, in Chinese real estate developer Logan Property Holdings. Kei Perenna's father Ji Haipeng is chairman and CEO of the firm.