They didn’t complete a single year of college, but Henrique Dubugras, 23, and Pedro Franceschi, 22, have already amassed a veteran’s share of Silicon Valley experience. Now they have the net worth to match. They are the founders and top executives of Brex Inc. a fintech startup recently valued at $2.6 billion, with an unlikely origin story. Dubugras was just 14 when he built his first company, the maker of an online video game, and shut it down after getting notices for patent infringement.