Jake and Callum Robinson: Twist in Aussie surfers' alleged murders in Mexico as a fourth person is arrested

• Fourth person has been arrested  
• Brothers Callum and Jake Robinson allegedly murdered in Mexico
• READ MORE: Jake and Callum Robinson are laid to rest on home soil in emotional funeral service

A fourth person has been arrested over the alleged murders of Perth brothers Callum and Jake Robinson, who were killed while on a surf trip in Mexico.

Brothers Jake, 30, and Callum Robinson, 33, and their friend Jack Rhoad, 30, had been on a surfing and camping trip in the Baja California region of Mexico, near Ensenada when they vanished on April 27.

Family and friends took to social media to ask for help to find them after they failed to check into their Airbnb in Rosarito, near the US-Mexico border.

A fourth person has now been arrested in connection to the alleged murders, after the brother's bodies were discovered 10 metres down a well, Nine reported.

The authorities have not disclosed any details of the man arrested.

The trio's bodies were found weeks after their disappearance near their remote campsite, with three Mexicans arrested soon after.

Police were able to make the initial three arrests after one of the brothers' mobile phones was turned back on and pinged a local tower.

A woman was found in possession of the phone as well as some illicit drugs.

She was arrested along with two other men.

The incident is believed to be a 'robbery gone wrong', with Mexican authorities alleging the three men were shot in the head by locals attempting to steal the tyres from their pick-up truck.

Jesus Gerardo, the accused ringleader of the trio also known as 'El Kekas', faced court and is set to remain behind bars until his hearing in November later this year.

Gerardo was arrested along with his brother Cristian Alejandro and girlfriend Ari Gisel.

The brothers were commemorated by their friends and family in a paddle out at Sorrento Beach, north of Perth this month, six weeks after they were killed. 

Hundreds attended the paddle out, heading out into the ocean on surf boards or boats and formed a circle with their oars in the air.

The Sorrento Surf Lifesaving Club posted on their Facebook page about the ceremony.

 'It will provide these communities with an opportunity to come together to commemorate and remember these two wonderful boys and show their support for their family,' the post read.

'WA surfers, surf life savers and ocean paddlers will all come together as one group as they paddle out to form a circle and remember Callum and Jake.'

Callum and Jake's mother, Debra Robinson paid tribute to her sons, along with her husband Martin at their funeral service in Sorrento in Perth's north west earlier this month.

They delivered an emotional speech to the 800 grieving friends and family watching the service, which was also live streamed.

'We loved that Jake was curious, kind and happy and never judgmental,' Mrs Robinson said.

'Callum always made a conscious decision to wake up and be positive every day.'

'He saw so much fun in life. We miss you beyond description, Callum and Jakey boy, please shine on us.'