It’s rare for identical twins to be so alike that even their parents can’t tell them apart, but Sophie and Megan Walker’s mum and dad struggled.

‘For about four months after they were born we had to keep a band around Sophie’s ankle because we couldn’t tell which twin was which,’ says mum Rebecca, as the sisters, now 16, roll their eyes in the way only teenage girls do. ‘I used to think that if we got them mixed up, who would know?’ admits dad Jamie. ‘At school, the teachers had no chance.’

The girls are still strikingly similar, with matching blue eyes, high cheekbones and tiny size six frames.

At the family home just outside Edinburgh, they sit on the sofa in unconsciously identical positions, knees hunched up under chins, hands crossed over shins in exactly the same way.

They share everything: clothes, sentences (one starting, the other finishing), a bedroom, a sense of humour.

There is one thing that now separates them, though. ‘We are not identical any more,’ says Sophie. ‘Because I have Cancer.’

If there is anything more heartbreaking than talking to a teenager who has been told she is old enough to make the decision about when her cancer treatment stops, it is this: having that conversation when the girl’s identical twin — perfectly healthy — is sitting beside her.

Not that conversation with these two ever stays downbeat for long. Can you joke about teenage cancer? They do.

Sophie tells me that there are upsides to having an identical twin when you go to pick a wig after your hair falls out due to chemotherapy.

‘I didn’t even have to show them a picture of what my hair was like before,’ says Sophie.

‘I just took Megan with me and said: ‘It was like that.’ ‘

When I ask Megan what it felt like to see her double without hair, Sophie leaps in: ‘She probably thought, “Oh, that’s what I’d look like bald,”‘ and her sister gives her a mock punch.

There is much of this sort of banter, which makes it easier for the adults in the room, in what is otherwise a nightmare parental scenario. ‘Every time Sophie relapses she asks for another pet,’ says Megan. ‘And when we go shopping she takes her wig off so she gets free make-up.’

These twins, and the cancer they don’t share, made headlines this week when it was reported that their symptoms — yes their symptoms — baffled doctors.

Astonishingly, when their long (and continuing) ride on the hospital rollercoaster began, it was originally only Megan on board. She was referred for tests in 2017 aged ten, when her parents started to worry about how pale and thin she had become.

The Walkers had always been a robust sort of family (there are ten children), but Megan was suffering from unexplained stomach issues and was finding it difficult to eat. ‘We thought she had an eating disorder,’ says Rebecca, 43.

‘I thought she was very young for that, but one of the older girls had said something about how Ariana Grande, the singer, was said to have had an eating disorder and Megan loved her.’

Megan is horrified — not so much about the eating disorder but the public airing of musical tastes. ‘I did NOT like Ariana Grande,’ she says. ‘Yes, you did,’ says Sophie.

Their mum takes up the story. ‘We were going backwards and forwards to the hospital with Megan and one day I was actually in the hospital with her when I got a call from home to say that Sophie was being violently sick.’

They ended up in A&E — with Sophie. ‘I could actually feel a mass in her stomach. I said, ‘stop tensing, Sophie’, but she wasn’t. Doctors kept flooding into the room, asking: ‘Any sign of weight loss, any pains over the last weeks or months?’ I was so confused, saying, ‘Not with Sophie, but with her twin — yes’.’

A biopsy confirmed that Sophie had a rare cancer called Wilms tumour, that affects mainly children. 

Rebecca remembers breaking down at the news. ‘I ran to the toilets and collapsed. The cleaners came through and helped me up’. Then there was a horrifying period where a chest X-ray on Megan flagged up something that needed further investigation.

Rebecca recalls: ‘I remember driving to my mum’s house and having a panic attack.

‘I was saying, ‘I cannot do this. I cannot do this. I cannot cope with both of them with cancer’.’

Thankfully, tests confirmed Megan at least did not have cancer. To this day, she is healthy, but they still do not know why Megan displayed worrying symptoms first.

‘At one point they actually had two different consultants — Sophie a paediatric oncologist and Megan a general paediatric one — who would liaise,’ Rebecca says. ‘One doctor eventually said that it must just be a ‘twin thing’, because they really didn’t know.’

Despite having undergone three apparently successful treatments, Sophie’s cancer has returned each time. She is very frail, but then Megan is slight too.

‘We don’t know why this is either, but their weights have always been in sync,’ says Rebecca. ‘When Sophie lost weight because of the treatments, so did Megan. When she put it on again, so did Megan.’

There is much of the medical side of this story that defies logic or explanation, but what is incontestable is that Megan has been with her sister throughout. ‘Holding her hand?’ I ask, trying to be gentle. ‘Eewww, no,’ says Megan. ‘No. Just telling her that she smells or something.’ 

Back we go into hilarity, with them explaining that a particular stem cell treatment involves chemicals that leave everything — hospital room, bedclothes, patient, even visitors — smelling of sweetcorn. ‘It was one of the worst bits of everything,’ says Sophie. ‘The sweetcorn phase.’

Further cajoling reveals that Megan has spent the last six years either curled up on a hospital bed beside her sleeping sister, sorting out her Spotify, or running to the hospital shop (‘they have an M&S, so it’s great’).

She tells me she plays Sudoko when Sophie goes for a procedure. Inevitably both have missed great swathes of school.

Her mum says: ‘Megan has been with her more than we have. At one point she didn’t leave the hospital for four weeks. I’d say, ‘Megan, do you want to go home? You need a break from this’ and she would say, ‘no’.

‘When Sophie has been too weak to speak, it has been Megan who understands what she wants.’

Megan quibbles with their mother’s theory about a secret communication. ‘Well, how do you explain the fact that you knew, on that day, that she wanted her socks on? None of us knew that!’

Neither twin thinks their story is particularly remarkable and both seem a little bemused by the interest in them.

They miss nothing, though. At the end of my day with them, when their parents have poured out all the despair in the world (‘you normalise it during the day but at night you wake up gasping for breath,’ says Jamie), I ask them how they think their mum and dad are coping. ‘Not very well,’ says Megan.

Who can blame them? The adults have concerns about both girls — Sophie for the obvious reasons; Megan for less life-or-death matters. ‘We’ve tried to make her go to school more, but she doesn’t want to go without Sophie.’

Sometimes the outwardly flippant approach of the girls drives their parents nuts.

‘They went through a phase of watching all the teen cancer films and they’d find it hilarious when we inevitably ended up crying,’ says Rebecca.

Quite how this family holds it together is beyond me.

As well as the twins, they have eight other children — James, 20, Emily, 19, Ruthie, 17, Daniel, 13, Olivia, 11, Emma, nine, Nathan, eight, and eight-month-old Evan, who is kicking in his babyseat with not a care in the world.

They all try to count up the number of chemo treatments Sophie has had and the girls quickly run out of fingers.

It comes down to this: over the past six years, Sophie has had nine separate types of chemotherapy and approaching 50 courses. There have been three major surgeries, including the removal of a kidney. Cancer treatments are tough on every major organ.

She has heart issues, her liver is damaged, her remaining kidney is working at a reduced efficiency.

Her fertility is compromised and though she has had ovarian tissue removed which may give her the chance of motherhood later, they are at the point where chat of ‘later’ has begun to seem a bit fanciful.

In March things were looking very dire. A scan revealed evidence of ‘active cells’. The family are used to this: the cancer returning.

But this time they were called into the hospital to be told that the chemo Sophie was on needed to be reduced. From here on it would be oral chemo only — ‘which means it is palliative,’ says Rebecca.

Sophie says: ‘I knew it was bad because they told us to come in. They never give the bad news over the phone.’

Rebecca says some of the medics in the room had clearly been crying. ‘We’d been planning a holiday to Florida but we weren’t going because of how Sophie was.

‘Then the consultant said, ‘go on the holiday’.

‘I fled the room but our nurse told Jamie, ‘go on holiday NOW, to make memories while you can’.