A woman who secretly committed child sex offences against four members of her own family, including her son, left her victims sad, angry and suicidal, a Cairns court has been told.

Key points: The woman was jailed for more than nine years with no parole date set

The woman was jailed for more than nine years with no parole date set Justice Dean Morzone described the defendant as complex and troubled

Justice Dean Morzone described the defendant as complex and troubled The court heard the lives of the young victims had fallen apart

Neither the woman, 45, nor her victims can be identified for legal reasons.

The victims — three of her nephews along with her son — were aged 9, 10, 12 and 14 when the offences began in the town of Mossman.

The District Court in Cairns heard graphic details of the children's involvement in various sex offences.

The woman's offending began against her son in 2013, then involved the other boys from about 2016.

Crown prosecutor Nathan Crane told the court it frequently took place on school holidays, while the boys were in her care, and sometimes occurred in full view of the others.

"Primarily, the sexual interest or the physical conduct was manifested through the younger children," Mr Crane said.

"There's an increased level of sexualisation of the children as the offending went on."

He said the victims were told the offending was "top secret" on some occasions, and that one boy did not want to participate but "complied because she is a trusted family member and he just does what she says".

The youngest boy, who was twice raped, was threatened that he would be exposed on Facebook if the matter became public.

The court heard parents became aware of the crimes after one of the boys revealed them earlier this year.

The woman pleaded guilty to 14 child sex offences, including two counts of rape.

Defence lawyer Bebe Mellick said his client's rehabilitative prospects and her early guilty plea should be taken into account, arguing for a parole date of two-and-a-half years.

But Justice Dean Morzone said he found it difficult to assess the risk of reoffending.

He described the defendant as a complex person who suffered a troubled upbringing, was diagnosed with autism spectrum disorder, excelled at various jobs and charity work, and received a Duke of Edinburgh's Award in her youth, yet committed what he called the most violent kind of offending.

"Your offending was secret and concealed, using multiple methods to decoy," Justice Morzone said.

"Your coercion was subtle, marked by manipulation and predatory grooming."

He sentenced the woman to nine and a half years in prison and set no parole date.

'We invited you over for Christmas'

In harrowing victim impact statements read to the court, the nephews' mothers said they had witnessed their worst fears realised as their children rapidly and inexplicably deteriorated into people they no longer recognised.

"(My boy) used to be a funny, cheeky boy known for his goofy facial expressions and sharp wit," one mother said.

"He is now a sad, suicidal and angry child who does not trust adults, except those who have proven themselves safe in his eyes.

"He may never become the person he was supposed to become because of the defendant's actions.

"You are the worst kind of predator — the predator we invited over for sleepovers and for Christmas Day; the monster who bought my kids treats and invited them to stay over at your house."

The mother of another victim said her life had fallen apart as she sought extensive specialist help, mystified as to why her son suddenly became anxious and depressed, behaved recklessly and no longer engaged with schoolwork and his peers.

His grandmother later discovered him attempting suicide.

"It all makes sense now, in hindsight [and the offending] makes you nothing short of a monster," she said.

Mr Crane told the court the woman's son still maintained that nothing happened, which he described as "a sad element".

"That realisation will come later," he said.