Tiahleigh Palmer's foster brother lodges appeal over sentence

The foster brother who had sex with Queensland schoolgirl Tiahleigh Palmer before she was allegedly murdered has filed an appeal against his sentence.

Trent Thorburn, 20, was sentenced to four years in jail after pleading guilty to incest, perjury and attempting to pervert the course of justice.

He has already spent nearly a year in custody and will be released in late January 2017, after serving 16 months.

Thorburn lodged an appeal in the Supreme Court on the grounds his four-year sentence was 'manifestly excessive in all the circumstances'.

Tiahleigh's body was discovered on the banks of the Pimpama River on the northern end of the Gold Coast on 5 November, 2015.

Her foster father, Rick Thorburn, has been charged with the 12-year-old's murder and is awaiting trial.

At Trent Thorburn's sentencing hearing, Judge Craig Chowdhury said when Trent revealed to his mother that he had had sex with Tiahleigh it 'became the catalyst for her tragic death'.

Judge Chowdhury told the hearing Thorburn's initial explanation that Tiahleigh had blackmailed him into having unprotected sex, or else she would hurt his dog, sounded 'completely implausible'.

The court heard Thorburn had concerns his foster sister was pregnant because she had been complaining about stomach pains.

'It seems that this fear of pregnancy triggered this extraordinary situation', Judge Chowdhury said.