For most people in their 20s, life's good as long as there's at least a fiver in their bank account for a pint.

Not for 27-year-old John Collison, though. He's worth a whopping $1.1 billion (£830 million), making him the world's youngest self-made billionaire.

Along with his older brother, Patrick, who's 29 and the third youngest self-made billionaire in the world (Evan Spiegel, 27, the co-founder of social media app Snapchat, is the second-youngest), John set up San Francisco-based company Stripe. Which, although you might not have heard of it, is worth some serious wonga.

You're probably expecting the brothers to be the sons of some loaded Manhattan socialite, but the LADs actually grew up in a small village in County Tipperary, in the Republic of Ireland.

After they finished secondary school, John and Patrick both decided to head stateside for their education, as they were both into computer programming as teenagers. Patrick was accepted at the prestigious Massachusetts Institute of Technology near Boston in 2007, and two years later John successfully applied to study at Harvard.

Deliveroo is one of Stripe's 100,000 global customers. Credit: PA

But, even before they'd finished uni, the brothers had already become millionaires with their first business venture, Auctomatic, a software company that enabled small firms and sole traders to trade more easily on eBay. They sold that business for $5 million (£3.78m) but the best was yet to come.

They then dropped out of university to launch Stripe in California's famous Silicon Valley. The company now has more than 100,000 customers across the world, and last year it was valued at a sweet $9.2 billion (£7 billion). Christ on a bike.

The company isn't widely known because it doesn't sell anything that customers can buy. Instead, its software systems enable companies to accept online payments and run their websites more easily.

So it must be a life of fast cars and holidays in the South of France, right? Well, apparently not.

Going for a jog is a lot of millennials biggest achievement of the week, but we're guessing if you're already a billionaire a regular run is probably, erm, a walk in the park.