They look like peas in a pod, but two of these four sisters are living with a condition so rare it has no name.
Violet and Nell Ford are believed to have the exact same genetic condition, but their parents have been forced to accept they may never know what it is.
Parents Rachael and Dave, from West Denton , welcomed their first daughter Edith into the world eight years ago, followed by Violet 18 months later.
Their family was completed two years after that with non-identical twins Alba and Nell.
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But while Alba and Nell are the twins, it's Violet and Nell that share the bond of an undiagnosed condition, which has so far left doctors baffled.
The girls are among thousands of children affected by a syndrome without a name (SWAN).
"It was a completely normal pregnancy with Violet, but she wasn't hitting her developmental milestones - she didn't take her first steps until she was three," said Rachael, 39.
"Because she was the second child, at first we just thought 'she'll catch up'.
"It was only when Nell started showing the same symptoms we started to think there was something else going on, that it might be all part of a bigger picture."
Violet and Nell have the exact same symptoms, including hyper-mobility, low muscle tone, unexplained episodes of hypoglycemia and learning disabilities.
But although they are believed to have the same condition, it is so rare it does not have a name.
"We've had to accept that we might never have a reason," said Rachael.
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"A geneticist from the Centre for Life believes they do have a syndrome of some description but they don't know what it is.
"I wouldn't change a hair on their heads, they're such lovely little girls.
"We celebrate milestones later than your average child but that just makes them being reached even more special, for example Violet at seven has recently been toilet trained, this is so wonderful and every toilet trip still gets a high five. Nell at almost five has just mastered jumping, the first time I saw both feet leave the ground together was fantastic."
The family have taken part in the 100,000 Genomes Project is mapping the genomes of tens of thousands of patients with rare diseases and their relatives.
Rachael said: "They look for genetic spelling mistakes and they can compare if the girls have the same one, and if Dave and I have it as well.
"We've only been in it since September, so we'll probably be some of the last to get our results, and it could still come back with nothing."
It’s estimated that 500 babies a month are born with an unidentified syndrome, often leading to isolation for them and their families.
"At first we felt really alone and isolated," said Rachael.
"We didn't realise there were other people out there who didn't have answers or explanations to their children's difficulties."
The family were handed a lifeline when they heard about SWAN UK, a support network for families affected by undiagnosed conditions.
Once a year this community of often isolated parents and carers come together for Undiagnosed Children’s Day at the end of April to highlight the needs and courage of their children. This year’s theme will be lions to focus on the bravery shown by children and young adults along with their siblings.
And on Saturday, Rachael and 30 other people will be gathering at Newcastle Racecourse in High Gosforth Park to take part in a 5k inflatable obstacle race for a major fundraising event which aims to raise awareness as well as money.
To donate to the appeal go to https://www.justgiving.com/fundraising/rachael-ford19 .
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