AAP

A private remembrance ceremony has been staged at the northern Sydney home of the Lin family to mark 100 days since their horrific murders.

Photographs of Min "Norman" Lin, 45, and Yun Li "Lily" Lin, 43, brothers Han "Henry", 12, and Tian "Terry", nine, and aunt Yun Bin "Irene" Yin, 39, were placed in every room of the North Epping property where they were beaten to death on July 18.

"It is a very private ceremony, personal," a family member told AAP.

Mr and Mrs Lin's 15-year-old daughter, Brenda, who was on a school trip to New Caledonia when the murders took place, is said to be very attached to the photos and regularly spends time poring over them.

Her grandparents, Yagfei Lin and Fengqin Zhu, and other family members conducted the ceremony a day after renewing their public appeals to help solve the shocking crime.

They visited the Epping newsagency owned by the family to speak with customers on Sunday before moving on to Chinatown.

Epping MP Greg Smith is convinced people, probably within the Chinese community, know who killed the family but are too scared to tell police.

"There are probably people in the community who may know something as to the motives of these people, but they are too scared to come forward because of the brutality that's been demonstrated," Mr Smith told AAP.

"The police are doing a very thorough job. They are determined to solve it.

"It's taking longer than these things sometimes do because of the limited evidence.

"It's very difficult, there were no bullets and very little in the way of forensics. But I'm confident it will be solved."

A dedicated team of 18 detectives is working on the case but no motive has been established and no arrests have been made.

Police are making no further official comment on the case other than to say inquiries are continuing and to urge anyone with information to contact Crime Stoppers on 1800 333 000.