3. The Collison Brothers

John and Patrick Collison of Stripe. Photo: Dai-Lon Weiss

What do you do when you’re barely 30, a paper billionaire and it still all looks to be upside from here?

Patrick (31) and John Collison (29) lead relatively modest, quiet lives. The elder of the two has taken to social activism, part time, on the issue of planning and affordable housing.