While the pair have a background in manufacturing - their grandfather founded Hurricane Wire Products and their father, Peter, was behind PEL Industries, an electric fencing company - neither knew anything about brewing.
The Ullrich brothers were attracted by trends in the New Zealand beverage industry. They also admit it's every Kiwi guy's dream to create a beer brand.
They could see potential in using some New Zealand knowledge and talent in the production, packaging and marketing areas.
The distinctive turtle logo is the work of Auckland-based design company Fracture and the beer recipe is from New Zealander Brian Watson.
"We're using New Zealand hops and malt and so forth but not getting tied up with thinking you need to actually manufacture here."
Ullrich says manufacturing in Fiji is not without its trials, but once you learn to work the Fiji way it is a friendly and helpful business environment.
"I think the challenge Fiji has is more of a challenge of any developing country. There is a lot of bureaucracy and systems that make things difficult for business and slow things down, but at the same time there seems to be a real willingness up there to really try to overcome that."
What they haven't been short of is skilled technical and science graduates needed to staff the brewery.
Although Jonathan, 35, lives permanently in Fiji and Jeremy, 39, commutes every two to three weeks, they initially thought they'd need an expat in Fiji full time and hired someone to work there on a six-month contract.
"We've employed some very bright, articulate, very good young people and we actually found within six or seven months we were able to localise it."
Vonu Pure was launched in bars and resorts around Fiji in late 2009 but there were some worrying moments along the way.
The original, seemingly cheap-as-chips manufacturing site on the outskirts of Nadi was submerged under 4m of water and sewage in a tropical deluge.
Fortunately, the search for an alternative factory on higher ground saw them chance on a building that was originally intended as a brewery before the project was abandoned.
A more costly mistake occurred after the first batch of beer reached the shelves.
Originally branded Taki beer (taki is a Fijian term for social drinking) the local trademark office missed paperwork showing the name was already registered to brewing giant Foster's. With the product out on the shelves a letter arrived from Foster's threatening to sue. The brothers felt like packing it in but their father told them not to worry - get the labels off, dump everything, and move on.
It was a costly mistake, in the region of $30,000 to $40,000, but in hindsight it resulted in them coming up with Vonu, named after the local vonu dina turtle, and a much stronger brand.
"If you can overcome things like that you kind of feel you can overcome anything," says Jeremy.
"I mean, getting a letter saying they were going to sue you to kingdom come. We just thought we were absolutely stuffed."
Success in the local Fijian market has come quickly.
Popularity with tourists saw it become the No1 premium beer within 12 months of launch.
Deals signed with big American distributors, the key to unlocking the lucrative US market, will see Vonu available in bars and supermarkets in Hawaii and California before the end of the year.
The Ullrich brothers say the plan is to prove the brand in those markets before scaling up with a $30 million investment partnership with a big beverage company.
New Zealand drinkers will have to travel to Fiji to sample Vonu Pure, which is unlikely to be available in this country for another year.
Jeremy Ullrich says the past three years have been challenging but worth it.
"In reality, if it was easy to do in Fiji 10 other people would have done it. It is a natural barrier to entry and I think that is what excited us as well."
