Who are New Zealand's richest siblings, Zuru owners Mat and Nick ...

They're the richest siblings in New Zealand, but how much do you really know about the Mowbrays?

Mat and Nick Mowbray have beaten long-standing richest man Graeme Hart to thetop of the NBR Rich List.

It estimates they are worth a combined $20 billion, compared to Hart's $12.1b - although the NBR's co-editor Hamish McNicol says even that might be underestimating them.

Turns out, there's more to the story than just those colourful little balloons that litter gardens across the country every summer.

Here's what you need to know.

Who are they?

Brothers Mat and Nick Mowbray wholly own Zuru - a toy, consumables and potentially construction firm.

Their sister, Anna, was previously an owner but she has since left the business with what she has described in media interviews as a "significant cash out" and has started a new recruitment app, Zeil. It's been billed as Tinder for jobs.

Nick Mowbray and his partner Jaimee Lupton also cofounded Monday Haircare.

Where are they from?

The siblings grew up near Cambridge but they now own the former Kim Dotcom mansion in Coatesville, Auckland, which they bought in 2016 for $32 million.

Anna Mowbray has also made headlines over her plans to put in a helipad on her property on the waterfront of Auckland's Westmere. She owns it with her partner, former All Black Ali Williams.

How did they get started in business?

A science fair hot air balloon kit made by Mat from a coke can and a plastic bag is part of Zuru lore.

It was the first of their constructions, and they began making and selling more of them, eventually getting them into local shops.

In the early 2000s, Mat and Nick - dropping out of university where he was doing a law degree - decided to go all-in and moved to a remote part of Guangzhou, China, where they began manufacturing toys.

Anna followed a few years later. The siblings tell the story of doing it tough for several years - including sleeping under a table in the Hong Kong showroom - before they managed to get a break when Walmart took an interest.

How much money do they make?

In an interview with the NBR, published last week, 39-year-old Nick said Zuru was on track to hit $3b revenue this year, with a plan to grow to $10b of annual turnover within the next five years.

Apart from a $20,000 initial loan from their parents, the business reportedly has no outside investment.

On the website NZ Inc, it says Zuru has opted for "an organic growth strategy that has seen the business finances completely internally".

What do they make?

Yes, Zuru is responsible for those Bunch O Balloons water balloons that fill up from your garden tap en masse. But its breakthrough hit was the Robo Fish, a toy fish that moves when it hits water.

Zuru also produces X-Shot guns and Rainbocorns.

Lately, Zuru has been branching out into other areas. Zuru Edge produces consumer goods such as pet care, beauty, baby care and health and wellness products. Zuru Tech is a project aiming to automate property construction.

Why have they been so successful?

Chris Wilkinson, from First Retail Group, credits the Mowbrays' "tenaciousness".

"Right from that story when they set up in Hong Kong - they camped in their office, they chased those opportunities, they knew they needed to be in that area because that's where the buyers were for those big brands.

"They've done some edgy things too, potentially crossed a few boundaries with the likes of Lego at various stages,. They've had some distinct wins, they've captured people's imaginations. They've used those to strategically engage the eyes, ears and hearts of the big brands - the Walmarts etc - once they've got them they've had the tenaciousness about keeping those relationships."

He said the Zuru US office was in Bentonville, where Walmart is also headquartered.

"That reflects the scale of that customer to their overall business."

Bodo Lang, a marketing expert at Massey University, said Zuru had a pattern of entering categories it expected to be able to disrupt.

"They conduct research into product categories where they believe they can provide value for consumers. This value may mean lower prices, and/or better quality. Once they have identified such an opportunity their other strength comes into play: efficient production.

"My understanding is that in the early days, Zuru used to outsource production. However, more recently they have focused on developing their own production facilities and making these highly efficient. Either way, not being weighed down by traditional production systems allowed them to be lean and mean in the early years and that has helped to re-invest capital into new product development and marketing. So there is a focus on continuous innovation.

The last piece of the puzzle is ambition. The owners of Zuru have been outspoken about their ambitions to be "the next Apple, Google, or Tesla". And the comparison is valid: ambition, marketing, and innovation are all aspects they share with these giants."

What are the controversies?

In 2022, Zuru won a court case against Glassdoor. A Californian judge said the company had to reveal the identities of people who posted negative reviews about Zuru as an employer. The court found that because the employees were most likely New Zealand citizens, they could not rely on US free speech laws.

In 2023, it lost a legal fight with Lego. It had been making claims on its packaging that its cheaper plastic blocks were compatible with Lego, which Lego said was infringing on its trademark.