Hitting the charts at No. 21 with $22.8 billion, Google co-founder Sergey Brin is currently focused on a variety of Jetsons-style technologies such as driverless cars. His role at Google is mostly focused on special projects while Larry Page tends to the ongoing business at hand. Brin and his wife have additionally been active in philanthropic pursuits, and, according to Forbes, have donated more than $5 million to the Parkinson's Institute. Meanwhile, his wife runs a biotech startup focused on using individuals' DNA as a means of identifying and addressing potential future health issues.