The woman, who cannot be identified for legal reasons, is a prosecution witness in Mr Xie's trial for the murders of five members of the Lin family of North Epping in the early hours of July 18, 2009.

The Crown alleges that, in the 12 months before the alleged murders, Mr Xie "groomed" his young relative.

After the killings, Mr Xie allegedly began sexually abusing her on a regular basis – as often as twice a week – over a 20-month period.

The female relative did not make the allegations of sexual abuse until May this year.

"It wasn't too bad a relationship, I loved hanging out with him, I loved talking to him, but it just wasn't particularly close," the young woman told the court of her interactions with Mr Xie before the family was killed.

"I still enjoyed his company.

"He was really talkative ... I felt like he paid attention to me, he was great to be around ... all of that stuff."

Mr Xie watched intently as the young woman gave her evidence, but showed little emotion.

The Crown alleges that Mr Xie twice engaged in "inappropriate sexual behaviour" with the woman before the murders, which indicated he had a "clear sexual interest" in her.

Mr Xie is accused of murdering Min Lin, 45, Mr Lin's wife, Yun Li Lin, 44, their sons Henry, 12, and Terry, 9, and Mrs Lin's sister, Yun Bin "Irene" Lin, 39, with a hammer-like weapon as they slept in their North Epping home.

The 50-year-old, who is married to Mr Lin's sister, has pleaded not guilty to all five counts.

The Crown alleges that the abuse of the female relative was part of his "sexual motive" for the crime.

It alleges that he was also motivated by a desire to get the Lin family's money and resentment over a "loss of face" in the eyes of Min Lin's parents.

The trial continues.