Ms Sidon, also known as Linda Jackson, was born in New Zealand and raised in Mosgiel near Dunedin.
She moved to Australia in 1981 and became a citizen three years later. Daniel was born in Australia, but it is understood his mother no contact with his father since he was a young child.
Ms Sidon and her son were living in a Housing Commission house at the time of her disappearance.
She was "socially isolated" but worked part time as a cleaner and had a few friends, police said.
Ms Sidon was last seen alive in June 2009 when she joined a gym near her home. Police say three days later was the last time her bank account was touched, the last "proof of life".
Initially it was thought that Ms Sidon, who suffered from anorexia, anxiety and depression, had either returned to New Zealand or taken her own life. She was listed as a missing person and while police say the investigation into her disappearance has been "ticking over" for the last six years, it wasn't until they received "specific" and "fresh" information in the last week that they ramped up efforts to find her.
They won't say what that new information is or who it came from but they now believe Ms Sidon was murdered and buried in bushland in the Numinbah Valley.
In late 2010 her father Garth Sidon called police in Dunedin and reported her missing.
Police there passed the information on to the Queensland missing persons bureau.
In November 2011 Mr Sidon died without any answers as to where his daughter was.
Her mother Eniz Murphy, who had remarried after separating from Mr Sidon was living in Nelson, also died not knowing. She passed away in March 2014.
Ms Sidon is survived by three sisters - Pauline, Jeanette and Pamela.
It is understood two of the women have travelled to the Gold Coast in the past to help police with the investigation.
The sisters did not wish to comment on this week's developments.
Pauline Sidon, who is understood to be overseas on holiday at the moment, told the Gold Coast Bulletin that she "did not wish to comment on the matter and neither would any other family members".
A spokeswoman for the agency that housed Ms Sidon and Daniel could not comment on how long he lived in the two-bedroom house after his mother went missing.
Nor would they say when they were alerted to the fact she was no longer living at the property.
"Unfortunately the department is unable to comment, as this is a current police investigation," she said.
The hunt for Ms Sidon intensified yesterday with rural fire crews joining police, excavators and specialist searchers to back-burn areas of interest.
Detective Superintendent Dave Hutchinson told the Bulletin it would make searching overgrown zones easier.
"Officers will need to wait for the sites to cool," he said.
"They will be guarded overnight and the search will resume tomorrow."
Mr Hutchinson said metal detectors and cadaver dogs had located areas of interest for the search.
He said earlier this week that items of evidence had been collected but refused to be drawn on what those were.
