A year on from the disappearance of their elder daughter, Kate and Gerry McCann are the most scrutinised parents in Britain. One of their children is the most famous little girl in the world. The other two are merely footnotes. What is easily forgotten in the analysis of their story is that there are three children, not one, in this family: Madeleine, Sean and Amelie. And like many children who lose a sibling, through death, abduction or family breakdown, the twins risk facing a double tragedy: that of losing their sister, and that of losing a childhood that had barely begun.
Whatever the outcome of the search for Madeleine McCann, the lives of her twin siblings changed irrevocably last May. Once, they were the babies of the family; now they are the family. Their mother was a working GP; now she is a stay-at-home mum who can hardly bear to be parted from them. For a year they have been living with a massive hole in their lives. Madeleine's pink bedroom is no longer off-limits, and they are now allowed to carry her dog-eared Cuddle Cat. But nobody is allowed to put on the little girl's clothing left behind. Friends say that Amelie looks agonisingly like her big sister.
When Natasha Lee heard about Madeleine's disappearance last year, she felt for Kate and Gerry, and particularly for their children. She was just seven when her two-year-old sister Katrice disappeared from a supermarket on 28 November 1981. The family was living in Germany, and had been out shopping for Katrice's second birthday party. "I saw my mum screaming and screaming," she says. "That will haunt me. I've never heard my mum cry like that ever, either before or since."
What followed Katrice's disappearance would traumatise any adult. That Natasha can talk about it now shows how well the family must have helped each other through the experience. At the time, however, her parents were far too distraught to consider the fragile emotions of the young daughter who was left behind. "Military police were going to turn up, and I went off by myself to search the underground car park," she recalls. "I told my dad, 'I can't find her.' I'll never forget the look on his face when he had to tell me that I wasn't going to find her. I couldn't really comprehend it as a child. Toys go missing – but then they turn up."
When a tragedy such as this happens, it is easy to imagine the parents' pain. But few people consider the long-term effect it will have on other children in the family. What many siblings of children who have died say is this: their parents, though devastated, had another child to love, to live for, to force them to get through. But their relationship with their sibling was unique; they will never have another like it.
In 2002, Gemma Dowler and her sister Milly were so close that they often used to bunk up in a bedroom together, even though they were 16 and 13 when Milly went missing. Over time, it became clear she had been abducted, and during the six months until her body was discovered Gemma had panic attacks, woke up screaming and couldn't sleep. She was terrified that the man who took Milly would be able to get into the house. But her mother couldn't bear to change the locks to comfort her – what if Milly tried to come home?
Leighanna Needham wasn't even born when her brother Ben disappeared in Kos in 1991, but his loss has cast a long shadow over her life. She now thinks of the huge-eyed boy in the photos as her younger brother. Their mum, Kerry, attempted suicide when Leighanna was a child, and temporarily walked out on her when she was two.
Vicky, Sharon Hamilton's younger sister, went missing in 1991 when she was 15. Their mother "died of heartache" two years later. Sharon was estranged from her dad, so she had to cope alone when her sister's body was found in the garden of Peter Tobin last November.
Of course, these incidents are mercifully, rare. But psychologists believe you can draw comparisons between these scenarios and the way a family would cope with bereavement.
"Parents are grieving and sad and will inevitably at some point be less emotionally available," says Dr Carol Burniston, a consultant clinical child psychologist. It is hard to imagine a parent in the midst of shock and grief like this being able to stop and think about the long-term development of their other children.
In the week after Katrice's disappearance, seven-year-old Natasha stayed with the family in the flat downstairs. "They tried to make everything normal for me. The little girl was my friend, but I didn't know why I was living with them, and it seemed as if I was away from my family for months. One day I knocked on our door to talk to my dad. Inside, it wasn't my home any more – it was dark, black, horrible. Mum and Dad eventually came to a decision that they also had me. I had to live as normal a life as possible."
According to Dr Burniston, this normality is crucial – just at a time when parents are least able to act normally around their children. "It's important to talk about what's happened as and when a child wants to – but also to protect children from adult information and speculation. I've seen children who have been very frightened by the news coverage about Madeleine. It's not just her parents who might now be tempted to over-protect their children, but every parent in the country."
Child abduction is rarer than you might assume, but there are many families in Britain living with an empty place at the table. And yet, says the charity Missing People, there is very little research into how relatives are affected when someone walks out or just disappears. The charity is soon to publish a qualitative study of those families who wait for news, and says that only then will we know what help they really need. One thing is clear from the tens of thousands of calls they receive each year: it's the not knowing that kills you. "People struggle with whether they should be hoping or not," they say.
Natasha Lee struggles with this, too. More than 26 years after her sister disappeared, when her mother's back was barely turned, nobody knows what happened that day or where Katrice might be now. But Natasha believes her sister is alive, somewhere. "I think she was abducted to order by a family who couldn't have children," she says. "I don't think about what might happen if she's found. She might not want to know us. It's probably the first time I wouldn't have anything to say."
When Natasha was 18, her parents divorced and the family left Germany. Unlike the McCanns, who once felt that coming home from Portugal would feel like giving up, she didn't find that a wrench. "That was only the place she went missing – my memories are still in my head." Nor are material things important – though Natasha still cherishes a small red cardigan, and remembers a pair of brown sandals finally being bagged up in a sack.
What is tough are all the special birthdays they will never spend together, and that sisterly bond that nobody can replace. It hurts to think about Katrice – but think about her, and talk about her, she does. "I wonder where she might be living, whether she has children. She'll be 30 next year. Does she look like me?
"I can't describe how proud I was to be a big sister," she says, after 26 years of not knowing. "I just miss everything. I miss Katrina. A piece of me is gone."
If you have any information about Katrice Lee or any missing person, please call Missing People on freefone 0500-700 700