Robert Alan Gee, 44, and 36-year-old Kristie Lee Willmott are charged in the June 14, 2021, death of her newborn son Michael Willmott.
He had suffered significant internal injuries and was later pronounced dead at the hospital, the police said.
Gee and Willmott appeared briefly at Beenleigh Magistrates Court on Thursday, where they were ordered to a commitment hearing on March 1.
Earlier, Detective Inspector Mark White said Michael died after suffering injuries from “significant force”.
“All I can say is that the medical examination of the child revealed significant internal injuries,” he told reporters.
“I don’t actually want to go into the details, it’s quite annoying.
“But it was absolutely clear, as at the end of the medical examination, what the cause of death was.”
White said the investigation into the boy’s death had been challenging for his colleagues “listening, reading this information and talking to people about it”.
He said the case had not been closed despite the murder charges and urged any witnesses or people who visited or lived at the caravan park around June 14 last year to contact police.
“Caravan parks have people coming and going… perhaps as residents, but also perhaps visiting friends,” White said.
“If someone might have been in and around there and we weren’t aware of it at the time, if they could come forward, or someone might know these two people and might have had conversations with them, we would be very interested to see what these conversations may have involved or worded.”