David Koch is dead at 79, his family announced on Friday.

The Koch brothers were two of the richest men in the world, with net worths of $58.7 billion each, according to Bloomberg.

net worths of $58.7 billion each, according to Bloomberg. Their fortunes came from their 42% stakes in the Koch family business, Koch Industries. Some of the company's best-known products include Dixie cups and Quilted Northern toilet paper. Koch Industries also refines crude oil and produces fertilizer.

Charles is the company's president and CEO; David had served as director emeritus, according to Forbes.

David Koch is dead at age 79, his family announced Friday.

Before David Koch's death, the Koch brothers were two of the richest people on earth. With net worths of just over $50 billion each, Charles and David Koch tied for 11th place on Forbes' March list of wealthiest people.

They have also been two of the most controversial billionaires, at least when it comes to their political contributions. Jane Mayer's 2015 book, "Dark Money," outlined how the two Kansas natives reportedly used their fortunes to forge a formidable web of political influence, with the intent of promoting their libertarian values.

Read more: Billionaire industrialist and conservative mega-donor David Koch has died at age 79

Still, that never stopped the Kochs from clashing with figures on the right, most notably President Donald Trump. The two brothers spoke out against Trump's tariffs in the past.

So how did the Kochs come to amass astounding wealth and wield such great influence? The answer lies within the history of their family business, Koch Industries.

Here's a look at how the brothers became billionaires in the first place.