It was 2009 and the high school student was preparing to fly to New Caledonia for an excursion, and looked around the departures gate to see her classmates kissing their families goodbye.

"Being a prideful teenager I did not say anything to my father, I just stood there awkwardly and thought to myself 'It is just going to be a week, I am going to see them again really soon,' " Ms Lin, now in her 20s, told the sentencing hearing for her uncle Robert Xie last week.

But while she was overseas, Xie murdered her entire family - her father Min "Norman" Lin, her mother Yun Li "Lily" Lin, her aunt Yun Bin "Irene" Lin, and her two little brothers Henry and Terry - in the bedrooms of their North Epping home on July 18, 2009.

"To this day, my biggest regret was not hugging [my father] and telling him I loved him, to say thank you for being an amazingly loving and caring parent," Ms Lin said.

Ms Lin's story as the only surviving member of the Lin family - and the sexual motive behind the killings - can now be revealed as she has given her consent to be identified by participating in an interview with Channel Seven's Sunday Night program, which has been promoted on television and online.

The court heard that Xie touched Ms Lin inappropriately  before the murders, but his assaults escalated when she moved in with Xie and his wife Kathy Lin after her family was killed.

Ms Lin told court that Xie sexually assaulted her regularly until he was arrested and charged with the murders in May 2011.

Prosecutors argued Xie's sexual interest in Ms Lin was one of the motives for the murders because he could have complete access to her with his in-laws dead.

The trials heard Ms Lin's bedroom was left undisturbed on the night of the murders.

The evidence that the killer seemingly knew Ms Lin was away, and knew the layout of the Lins' house, helped police focus on Xie as a suspect.

Xie also offered to adopt Ms Lin in the hours after the murders, the court heard.

Xie has not been charged over the alleged assaults.

The juries in Xie's four trials knew of Ms Lin's evidence, but journalists could not publish anything that identified her due to laws protecting children involved in crimes.

Justice Elizabeth Fullerton said she accepted the evidence of Ms Lin, referred to as Ms AB, when sentencing Xie to five life sentences earlier this week.

"The risk that this offender may commit offences of violence in the future, and the community's legitimate expectation that it is protected from that risk, is amplified by the sexual violence the offender inflicted on Ms AB after the murders, as the surviving member of her family."

After two aborted trials, and a third trial that ended in a hung jury, a fourth jury found Xie guilty last month.

Xie and Kathy Lin maintain he is innocent.

In the victim impact statement Ms Lin read to the court, she told how the loss of her family had impacted every part of her life.

"It has been 7½ years since I have lost my family. That's 7½ years without a loving mother, 7½ years without a loving father, 7½ years without two exuberant brothers who were my best and closest friends and 7½ years without an extremely kind aunt.

"In this time I have finished my HSC, was accepted into uni, got my first part-time job and learnt to drive. But I have achieved all these things without my family beside me.

"These inherently happy moments are now at most bittersweet, they have now become a painful reminder of the family I have lost and I will never see again."