The man, who cannot be named in order to protect the girl's identity, told police he saw the girl as his partner and raped her "whenever he had the chance", resulting in years of sexual abuse that only ended following his arrest in November last year.

However, in a sentencing hearing in Wollongong District Court on Friday, the man made the extraordinary claim that he was "not a bad man" and hoped one day to reconcile with his estranged family.

"I'm not a bad man like other people you see in here... I'm a good man whose just made bad mistakes in my life," he said in a letter tendered to the court.

"I hope you give me another go to improve my life."

However, Judge Andrew Haesler was critical of the man's lack of remorse, noting he had no insight into his offending at all.

"He has no concept of the consequences of his actions," Judge Haesler said.

A set of agreed facts tendered to the court reveal the father began sexually abusing the victim, the oldest of three children, when she was nine years old and first raped her when she was in Year 3 at school, telling her it was normal for the oldest child to have sex with their father.

The now 16-year-old told detectives her father would stand in her room and watch her then ask if she "wanted it" and would keep watching her until she gave in.

She said she initially tried to push him away when he raped her but eventually learned not to because it would "pull and hurt down there" when she did.

The teen said her father plied her with alcohol on at least one occasion before raping her and gave her $20 another time to perform oral sex on him.

She said the abuse was so regular she had trouble recalling individual acts, but did say she remembered being raped at one stage in late 2018 while her mother - the man's long-term partner - was in hospital giving birth to her baby sister.

It's unclear how police became aware of the abuse but the girl gave a statement to detectives in November last year, resulting in her father's arrest. He has since pleaded guilty to a charge of maintaining an unlawful relationship with a child.

Meanwhile, police also interviewed the girl's mother, who told them her partner's sexual pursuit of their daughter was talked about as if it was a "known fact" within the household.

She said she had tried to stop the abuse by offering herself up to her husband for sex instead, but claimed he rejected her most of the time, saying their daughter was "better than her".

The woman said she had never witnessed the abuse first-hand but her husband had told her about it, implying he committed the offences because she (his wife) wouldn't have sex with him.

She admitted she had occasionally asked their daughter to have sex with her dad but claimed she was only acting out of "fear and pressure".

She said the girl usually refused but occasionally gave in in order to protect her.

The mother further admitted her husband sometimes asked her to leave the house so he could be alone with their daughter and while she tried not too, sometimes it was "unavoidable".

When asked why she hadn't reported the matter to police, the woman said she had been raped by her own father in similar circumstances as a child and her mother had tried to protect her in the same way.

She also said she was afraid what people would think of her and worried she would lose her children if she made the abuse known to authorities.

In court on Friday, defence lawyer Scott Fraser said his client had a borderline intellectual disability and would need professional and social support when he was eventually released from prison.

Mr Fraser said the man still had support from both his sisters and his mother, all three of whom were in court for the proceedings.

Judge Haesler sentenced the man to an overall prison term of 15 years, with a non-parole period of 11 years.

With time served, he will be eligible to apply for parole in 2030.