When Marieme and Ndei were born, they were expected to live only a few days.
Now seven years old, they are thought to be the only growing conjoined twins in Europe.
The two girls each have their own personalities and moods, but depend on each other for survival.
“When you are told from the beginning that there is no future, you just have to live in the moment,” said his father, Ibrahima.
Conjoined twins are rare, occurring in around 1 in 500,000 births in the UK.
About half are stillborn, and another third die within 24 hours of birth.
So seeing Marieme and Ndaye celebrate their seventh birthday with a large group of friends will not only please Ibrahima, but also the doctors who have been caring for them.
Marieme and Ndei share a pair of legs and a pelvis, but each has a spinal cord and heart.
They have 24-hour childcare and attend a regular school in South Wales with friends.
“They are fighters and they are proving everyone wrong,” Ibrahima said.
“My daughters are completely different. Marieme is very quiet and introverted, while Ndei is completely different and very independent.
“I'm not going to pretend it's easy, but it's a huge privilege. I feel lucky to witness this constant battle of life.”
When the twins were born in Senegal in 2016, their parents were expecting one baby. Doctors expected them to live only a few days.
“The only thing we can do is stand by them and not allow them to walk this journey alone. We know we are dealing with warriors who are clinging to life. It was clear to me from an early stage.”
Their best chance of survival was thought to be separation.
The family arrived in the UK for treatment at London's Great Ormond Street Hospital in 2017 after “begging” hospitals around the world for help.
Ibrahima had hoped that the famous children's hospital, which has separated more conjoined twins than anywhere else in the world, would be able to separate them and send them home to their siblings in Dakar, but it didn't work out that way. . .
Tests revealed that Marianne's heart was too weak for complex surgery.
Medical experts warned the family that if they did not separate, their daughter might live for more than a few months.
But doctors advised that separation would give Ndaye the best chance of survival.
Ibrahima said at the time: “It was killing my child for another child. It's something I can't do.”
“Right now, I cannot allow myself to choose who lives and who dies.”
Marieme, Ndei and Ibrahima remained in the UK for treatment as their mother returned to Africa to care for her other children, while the three moved to Cardiff.
A illuminating insight into the lives of 7-year-old conjoined twins who were expected to live only a few days.
Inseparable Sisters will be available to watch on BBC iPlayer from Wednesday and on BBC One from 22:40 BST on Wednesday. For viewers in Wales, it will be broadcast on Wednesdays at 20:00 GMT on BBC One Wales.
Ibrahima, a former managing director of a Senegalese travel agency, said, “It was very difficult for me not to be able to go home because I had family left and I had a job in my hometown.''
“It's an unknown world, but I didn't think too much about it and just followed my heart. It's a parent's responsibility to make sure there's someone here for them, and that's my purpose in life. ”
The twins are at serious risk of infection and heart failure and require regular hospital check-ups.
Dr Gillian Boddy, a consultant paediatrician at the University Hospital of Wales, said: “At first there was a bit of new excitement, but then we realized this was something we had only read about in textbooks.”
“Between them they have a pair of legs and a pelvis. If you move up their abdomen, you'll see a lot of different organs. We don't know exactly, but some parts are shared. , we know there are several separate parts.''
“They have two separate spinal cords with all their nerves, but somehow they're perfectly coordinated and they don't have to tell each other how to move their arms or how to move their legs, they just do that. It works.”
Dressing twins is difficult.
“I have to buy two identical tops and take them to an alteration shop to have them pieced together,” Ibrahima said.
“They have two legs so they can wear regular pants, but their hips are so wide that I have to take them to the store for replacements too.”
The family are now integrated into the Cardiff community and the twins are cared for day and night as carers help their father with respite support.
The sisters are in Year 3 at a local mainstream primary school, where they are supported by two classroom support workers.
“I want them to live normal lives, play and laugh with their children, make friends and grow as people,” Ibrahima said.
“They don’t have to hide from anyone and being in a mainstream school shows they are part of society and they are lucky to be part of this community.”
Marieme and Ndei's next challenge is to stand up and walk. They currently manage about 20 minutes every day with the help of a standing frame.
“They accomplished something that no one expected,” Ibrahima said.
“If you are told from the beginning that there is no future, you end up living in the present,” he added.
“We know that at any time we could get a call saying something bad happened.
“For how long? I don't want to know. We're going to make every day a surprise and celebrate life.
“There are times when I struggle, but despite all the challenges, I feel lucky. They bring me so much joy. It's a huge blessing to be their father.”