Madeleine McCann's two-year-old twin brother and sister have finally been told the heartbreaking truth about her disappearance.
Until last week, toddlers Amelie and Sean believed four-year-old Madeleine was "on a little holiday" and would be back soon.
But their parents have now broken the news that their big sister is "missing" and "Mummy and Daddy are looking for her".
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Madeleine, smiling in the centre, with her twin siblings Sean (R) and Amelie (L)
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The revelation added to growing signs that devastated Gerry and Kate McCann are planning to return home to Britain soon, perhaps as early as next month.
The traumatic task of telling the twins was undertaken on the advice of a child psychologist who recently flew out to the Algarve to help Kate and Gerry McCann choose the right words to explain Madeleine's continued absence, without frightening the twins.
A family friend said: "Kate and Gerry have taken the advice of child and trauma experts and have now told the twins that Madeleine is missing and Mummy and Daddy are looking for her.
"At the start they used to tell the children that Madeleine had gone on a little holiday but as time has gone on they have changed the language they use.
"At their age the twins understand the concept of 'missing' like a favourite toy they can't find - but they know it is much more serious because it is their sister and they miss her." Scroll down for more ...
Madeleine has been missing since May 3
Yesterday, Kate and Gerry McCann made their familiar pilgrimage to the resort's tiny whitewashed church to pray for their daughter's safe return. The twins stayed at the family's rented villa with visiting relatives.
The young children's routine was disrupted last week when the McCanns were asked to keep their children away from the Mark Warner-run creche because increasing media attention around the 100th day anniversary of Madeleine's disappearance was "spoiling" other children's fun. Now things have calmed down in the small town, Sean and Amelie have been invited back.
The McCanns say their children believe they are on one long holiday but the twins talk about their big sister frequently and with a "heartbreaking innocence".
In a recent interview, Kate McCann told how she is often caught unawares by one of their remarks.
The 39-year-old locum GP said : "When we went back to the UK for a family baptism there was an empty seat on the plane and Sean said, 'That's Madeleine's seat.' That caught me.
"It was a very emotional day. Amelie asked me afterwards, 'Where's Madeleine? I miss my sister'. It catches me."
The McCanns are now talking for the first time about ending their vigil in Praia da Luz and returning home to Rothley in Leicestershire. Scroll down for more ...
Kate and Gerry McCann have begun to prepare for the unimaginable: that they may have to return to Britain without Madeleine
The couple have extended the lease on their rented house, but only for a month, and some friends expect them to come home by the end of September.
Kate said earlier this week: "We know we will be going back and I guess one day we will wake up and it will be right. We never thought we would go before she came back. Now we just don't know but we have the twins to consider.
"I can't imagine how we came out as a family of five and going back as a four."
It is thought breaking the news of the hunt for Madeleine is part of preparing the twins for big changes ahead.
The McCanns asked for expert help in answering their younger children's questions and a British psychologist, who specialises in children under five years old, flew out to the Algarve to see the family.
A family friend said: "They are very mindful and careful not to upset them, and that is why they have taken advice on what is appropriate to say to two-and-a-half year olds and how to approach such a delicate and traumatic issue.
"It was to talk about the future and the psychologist spent some time with the twins. They are doing very well in all the normal things like potty training and learning new words.
"Kate and Gerry have always been very open with their children and the reason they got expert advice was because they wanted to do the best thing for the twins."
Sean and Amelie, who like Madeleine were born through IVF, have been encouraged to talk about their sister and often refer to Cuddle Cat being Madeleine's.
"They pick things up that they recognise as being Madeleine's.
"The children have always been very close and the twins were so excited when came on holiday because they got to share a bedroom with Madeleine. They were excited every night when they went to bed."
Detectives say the two children slept throughout the unexplained disappearance of their big sister on May 3.
The McCanns finally tell their twins Madeleine is missing | the Daily Mail