The rags-to-riches story of WhatsApp cofounder Jan Koum, who grew up without running water and is now worth over $9 billion

Reuters

WhatsApp cofounder Jan Koum.

Few people have benefited from Facebook's incredible success more than WhatsApp cofounder Jan Koum.

With an estimated fortune of roughly $9.5 billion, 41-year-old Koum has come a long way from growing up without running water in Soviet-Era Ukraine to creating a messaging app used by 1.2 billion people.

Facebook purchased WhatsApp in 2014 for a jaw-dropping $19 billion, adding Koum to the company board and sending his net worth into the stratosphere.

Koum now leads a team of around 100 people working on WhatsApp, which is used heavily in developing countries like India and Brazil. And he sold over half of his shares in Facebook last year, totaling roughly $5 billion.

Here's how Koum got to where he is today: