Stephen Grimmer has never given up hope that somewhere in the world his sister is alive and living a happy life with another family.
It has been more than 42 years since three-year-old Cheryl Grimmer was snatched from Fairy Meadow beach by an unknown man, with her family enduring many moments of false hope over the decades, including a ransom note, a lock of hair sent to police, and a coroner's inquest that ruled Cheryl was likely dead.
But Mr Grimmer, who was five at the time of his sister's disappearance, said he and his family would never stop believing that Cheryl was alive.
The children's father Vince died eight years ago, still wondering what happened to his only daughter, and their mother Carole is now very ill with emphysema.
"We will never give up hope," Mr Grimmer said.
"It's a shame dad is not around still to keep searching and keep hoping, but mum is never going to give up."
He said news of a NSW government $100,000 reward for information about the disappearance had buoyed his mother's spirits as her 70th birthday nears.
"When we had the coroner's case - that dampened mum's hope a little bit - but it's still on file in the cold cases and she is pretty happy about this announcement," Mr Grimmer said.
"It's great that they're doing this and that they are offering such a big reward because it means someone who knows something might come forward so we can either find out she is alive somewhere in the community or that she is dead."
"The only thing we can hope for is that someone does come forward, and hopefully this reward will help to widen the search nationally."
Mr Grimmer now lives at Mount St Thomas, and said Fairy Meadow Beach, where Cheryl disappeared, still haunts him.
"It's always on my mind, and whenever I go down to the Lagoon with my kids I always look across to the beach and the bushland that is there, and just wonder what happened," he said.
Fresh arrivals from Britain, Mrs Grimmer, her three sons and daughter had been swimming on the afternoon of January 12, 1970, before the children went to the change sheds to get out of their soggy costumes.
Carrying her swimmers and towel in a bundle, Cheryl was standing near a bubbler when witnesses saw a man pick her up and run into the car park.
At an inquest into her disappearance last year, a coroner ruled Cheryl had died soon after the man took her, but that the cause of her death was unknown.
The inquest heard a 2008 reinvestigation into the case looked into the possibility Cheryl was either killed and buried or kept by her abductor and brought up under another name.
At a media conference held in Sydney yesterday, Police Minister Michael Gallacher said the kidnapper could be elderly or dead, but the family still needed to know what happened.
"The release today of the reward is an incentive for people to come forward.
"But there's a bigger incentive - the bigger incentive is the family."