"They didn't show it outwardly, but it was hard on them."
Renewed efforts to solve the case in recent years had brought his sister's memory to the front of the mind, he said. "After so long I've got to confess you don't think about it every single day. But there's things that will happen and you might think about it for quite a few weeks on end.
"Over the last couple of years, I've thought about it an awful lot more than I had for a little while. It's certainly there."
Mr Davie's brother Nigel is at the inquest, which heard that Ms Davie was last seen by her boyfriend, Stephen Lavender, on April 6, 1980, when she visited him in hospital.
Mr Lavender received a hastily written letter from his girlfriend a few days later, which said she would be "going away for a few days", the Sydney Morning Herald reported.
It was the last time she was heard from, and police have followed a number of leads since without success.
One was a statement from a woman who said she had sat next to Ms Davie on a flight to New Zealand.
The woman said Ms Davie had told her she was sick of her boyfriend and was moving back home for good, but when police checked her details they proved to be false.
The inquest also heard that shortly before she went missing Ms Davie went to a Kings Cross nightclub with a friend. The pair met two "unknown males", one or both of whom invited Ms Davie on a trip to Melbourne with them.
Other friends of Ms Davie told the inquest she was extremely trusting and, at times, naive - something her brother agreed with.
"She was very trusting. She used to hitchhike all around various places in the world and New Zealand."
In April last year, Australian police offered a A$100,000 ($132,000) reward for information on the case.
In July, police released computer-generated images of two men Ms Davie had met at the Kings Cross nightclub to encourage them or other witnesses to come forward.
Mr Davie said anybody with any information about his sister should contact police. "Even if it was bad news, it would still be good news."
