'Live bigger, shine brighter': parents of slain brothers speak

Jake, 30, and Callum Robinson, 33, were on a surfing trip in Baja California with their US friend Jack Carter Rhoad when the trio were allegedly killed in a robbery gone wrong at their campsite.

Debra and Martin Robinson travelled to Mexico to identify the bodies on May 6 after their bodies were discovered in a cliff-top well.

"We know they were truly loved and impacted many lives," Ms Robinson told reporters in San Diego.

"Please, live bigger, shine brighter and love harder in their memory," she said.

She remembered Callum as being a "lovable, larger-than-life character" who enjoyed his life and career playing professional lacrosse in San Diego.

"His brother, Jake, was a happy, gentle and compassionate soul who was pursuing a career in medicine," she said.

"Jake's passion was surfing and it was no coincidence that many of the hospitals he worked in were close to surfing beaches."

Half a million dollars has been raised to support the grieving families of two Australian brothers and their American friend after the bodies of the three men were found in Mexico.

More than $450,000 has been raised in two fundraisers for the brothers across Australian and American GoFundMe pages with 3,200 people donating by May 8.

"Our hearts ache with grief for their families, friends, and community," San Diego-based GoFundMe organiser and friend of Callum JT FitzGerald said.

"Their presence brought immeasurable joy, love, and kindness to those around them, leaving a mark on our lives," he said.

"Martin and Debra are currently experiencing every parent's worst nightmare," the Australian fundraiser, run by Mr Robinson's coworker Brett Grocock, said.

The US fundraiser highlighted the expenses facing the Robinsons family including breaking their older son's San Diego lease and relocating his belongings to Australia.

Between flights, funeral costs and attorneys the Robinsons expect to be facing a bill of more than $130,000.

More than $80,000 has been raised to support Mr Rhoad's partner Natalie and keep his memory alive.

The donated funds will provide housing, food and transportation support "during this unimaginably difficult time".

The money will also be used to create scholarships in Mr Rhoad's name and for donations to causes he felt passionately about, the fundraiser said.

An outpouring of grief for the three slain men has erupted on social media after their bodies were discovered.

Callum Robinson's girlfriend Emily Horwath posted a number of emotional images and videos from friends of the happy-go-lucky lacrosse player nicknamed the "Big Koala".

"My heart is shattered into a million pieces. I don't have the words right now," she said.

"You are one of one. I will love you forever."

Prime Minister Anthony Albanese said his heart goes out to the brothers' loved ones.

"I've indicated that I wish to speak to them at an appropriate time of their choosing," Mr Albanese said.

Mexican authorities have arrested three people suspected of the murders.