Eighteen-month-old Ben disappeared on Kos on 27 April, 1991 while playing near a house his family was working on.
His parents, Kerry Needham and Simon Ward, are trying to rekindle interest in the case with a pounds 20,000 reward and a 24-hour telephone hotline in Greece.
They have returned to Kos accompanied by Ben's grandparents Eddie and Christine Needham. 'Even though we have a new baby, the whole family will never be happy and complete until Ben is returned to us. We want the people in England and Greece to know how much we love him,' Kerry Needham, 22, told a news conference in Athens.
She and Mr Ward, from Sheffield, have a five-week-old daughter, Leighanna. They have been searching Greece and the Greek islands since Ben's disappearance, but this is the first time the whole family has returned. They said they had been moved by the warmth of the local people.
'You can't explain in words exactly how you feel,' said Ms Needham. 'It's like somebody taking a piece away from you. You feel empty inside. You just want him to be there, everywhere he was before. On the beach. Everywhere you expect him to be. But he is not.'
Despite the long time that has passed since Ben was last seen, the family is vinced that he is still alive. His parents suspect that he may have been stolen and sold to a childless couple. 'We have been assured by Kos police that he is not dead,' said Ms Needham.
'They have searched many, many times and he is not there. The only explanation is that someone has taken him. We don't know where and we don't know why. And we need to know.'