Robert Alan Gee, 44, and 36-year-old Kristie Lee Willmott are accused over the death of her newborn son Michael Willmot on June 14, 2021.
He had suffered significant internal injuries and was later declared dead in hospital, police say.
Gee and Willmott appeared briefly in Beenleigh Magistrates Court on Thursday, where they were ordered to face a committal hearing on March 1.
Earlier, Detective Inspector Mark White said Michael died after suffering injuries from “significant force”.
“All I can say is the medical examination of the child disclosed significant internal injuries,” he told reporters.
“I actually won’t go into the details, it’s quite distressing.
“But it was quite clear, as at the end of that medical examination process, what the cause of death was.”
White said investigating the boy’s death had been challenging for his colleagues “to listen, to read this information and speak to people about it”.
He said the case hadn’t been closed despite the murder charges, calling for any witnesses or people who visited or lived in the caravan park around June 14 last year to contact police.
“Caravan parks have people that come and go… maybe as a resident, but also maybe visiting friends,” White said.
“If someone may have been in and around there and we weren’t aware of it at the time, if they could come forward, or someone may know these two people and may have had conversations with them, we’d be really interested to see what those conversations may have involved or articulated.”