Twin brothers Jonathan and Benjamin Siero bike through the Nullarbor

Jonathan and Benjamin Siero are used to doing things as a team.

The 32-year-old twins from Perth were born just 12 minutes apart and have fond childhood memories of being driven through the Nullarbor to visit relatives during the school holidays.

Now, as adults, they do it on bikes.

Her stepfather Sam was diagnosed with brain cancer last year and had just 12 months to live, so they decided to make the trip to raise funds for medical research.

“The diagnosis came as a shock to the family, so we decided to raise money [charity] Brain Cancer Collective,” said Jonathan.

The twins have raised $10,000 online so far.

Benjamin said her ailing stepfather Sam was deeply impressed.

“He has the facade of a grumpy old man, so when he shows any kind of warmth, you know it means something,” he said.

The 3,000-kilometer journey began on Monday and will last 34 days.

The brothers have had months of training to get to this point.

“I started running more each day to build my fitness, then switched to cycling and doing 25 miles each weekday to prepare,” Benjamin said.

The brothers’ biological father, Gerard Siero, drives as an escort for his sons.

He hauls a month’s worth of supplies in a Volvo sedan and keeps an eye out for trucks while communicating over the radio.

“We plan to stop at Bruce Rock, Moondie Rocks, just past Kalgoorlie, Widgiemooltha, about halfway through Norseman and Fraser Range and then Balladonia… the list goes on,” he said.

Their original goal was to raise $5,000, but now it is hoped that they will reach $20,000 before the journey ends.

Jonathan said anyone who lives along the Nullarbor is welcome to shout out a drink to the trio.

“We’re not going to say no, I’m definitely going to have a beer,” he said.

“Maybe a cup of tea for Ben.”

More information about her trip can be found here.