A Ballymoney family is raising awareness of the stem cell donor register - after their youngest son Caden was saved by bone marrow from his big brother.
Caden Moore was diagnosed with an ultra-rare condition called Very Severe Aplastic Anaemia (VSAA), which meant his body could not produce enough blood.
His only hope of survival was a bone marrow transplant; and thankfully his brother Ben, older by three years, was a perfect match.
The boys underwent the donor procedure at Bristol Children's Hospital in July 2017 and then Caden began a gruelling journey back toward health as his body worked to accept the new bone marrow.
Now aged nine, he is finally on the road to recovery - all thanks to his hero big brother.
Their mum Sabrina (42) says: "The boys were always close; Caden looks up to Ben and follows him around. But now they have an extra special bond."
Watching her eldest son Ben grappling his brother Caden into a headlock, Sabrina opens her mouth to scold them… then closes it with a wry smile.
They'd waited years for Caden to be well enough for a bit of rough and tumble. Not long ago Ben's bravery had saved his little brother's life.
"Nothing says I love you quite like a brotherly headlock," she laughs. "Caden's health has been so fragile for so long, it's actually lovely to see them playing together again as boys do."
The family's incredible ordeal began three years ago, when the normally energetic Caden, then six, became lethargic and out of sorts.
He and his siblings Ben, then nine, and sister Kaia, then 12, were very active and sporty, playing football and hockey.
Sabrina (42) and her husband Bryan (40), from Ballymoney, began to worry that Caden was struggling to keep up.
"He was always covered in bruises," Sabrina remembers. "At first Bryan told me not to worry - boys will be boys.
"He was always tearing around after Ben and Kaia. He idolised Ben in particular, wanted to do everything that Ben wanted to do.
"But one day he hid his hockey stick under our car so he didn't have to go to practice. He was too tired and just wanted to get into bed.
"As I helped him into his pyjamas, I gasped in horror. There was this huge purple bruise spreading the whole way across his back."
The following morning, June 4, 2017, Caden was admitted to Causeway Hospital in Coleraine for tests.
"His blood counts were so dangerously low that doctors said they didn't know how he was still functioning," says Sabrina.
"They said he had very few red blood cells, very few platelets and literally no white blood cells.
"My mind was reeling. At first I took heart that they were keeping him in Coleraine, because I knew really seriously ill children are often sent to Belfast. But then they were arranging an ambulance to transfer him to the Royal Victoria. That's when we really started to fear the worst.
"As soon as he got there he was put into isolation because his lack of white blood cells meant he would have no immune system. At that point doctors suspected he had leukaemia."
But test results showed something more surprising. Caden became one of just 150 people across the UK each year diagnosed with an ultra-rare condition called Very Severe Aplastic Anaemia (VSAA).
Put simply, his bone marrow wasn't working properly and his body wasn't able to make enough of its own blood. The number of stem cells in his bone marrow had fallen below 30%.
"He was literally running out of blood," explains Sabrina. "They immediately started giving him transfusions and put him onto the organ donor register. His only hope of long-term survival was a bone marrow transplant."
Doctors told Sabrina and Bryan that their other two children could be Caden's best chance of a match because they shared the same genetic make-up.
Bryan stayed with Caden in isolation in Belfast, while Sabrina drove home to Ballymoney to talk to Ben and Kaia.
"That was the hardest part," she recalls. "I sat them down and explained their little brother was very sick, but one of them might be able to help him get better. I told them it was entirely their choice, but they both said straight away they wanted to help."
Both children underwent tests and three weeks later the results came back.
"I got off the phone and just screamed," laughs Sabrina. "Ben was a perfect match. He'd been lying on the sofa watching telly; he jumped up and we both started running around celebrating."
In July 2017, both Caden and Ben were flown to Bristol Children's Hospital for the transplant.
Ben, then still just nine, underwent psychological assessment and counselling to make sure he understood what he was being asked to do and what the procedure would entail. Because he was so slight, doctors would need to take bone marrow out of each of his hip joints.
It was also essential he understood that there was a chance the transplant wouldn't work, and Caden's body might reject his bone marrow.
"The day of the transplant was the toughest day of my life," says Sabrina. "Both of my boys were sick, in different parts of the hospital. Me and Bryan were just shuttling between them.
"Ben was so brave, telling all the staff he was saving his little brother.
"Meanwhile Caden was desperately ill. Blood transfusions were the only thing keeping him alive. And we had no way of knowing whether the transplant would work or whether his body would reject it."
That uncertainty hung over the family for the next two years. At points Caden would rally, and they dared to hope he was recovering.
Then he'd suffer a relapse as his body fought to reject the donor cells. Strong drugs and steroids were used to suppress his immune system, meaning he lost his hair. "At times like those Ben would be inconsolable," says Sabrina. "He'd say to me, 'Mummy, why isn't my blood working for Caden?' It was so difficult. He blamed himself."
Finally, this year, Caden's condition has improved as his body begins to accept Ben's bone marrow. For the first time in years, Sabrina can watch her boys, now nine and 12, play rough and tumble with each other.
In April Caden had his central line for medication removed, meaning he could have a bath for the first time in three years - a big moment!
His immune system is still fragile so his family are being extremely careful during lockdown.
"Caden follows Ben round the house, he wants to be wherever his brother is," says Sabrina. "Sometimes Ben lets him put him in a headlock, just to be charitable, but usually it's the other way round.
"It's great to see them back to doing typical boy stuff though. They love watching football and playing video games.
"I think they've got even closer since the transplant. A part of Ben will literally be with Caden for ever now - so their bond is stronger than ever."
For more information about joining the stem cell register, to donate either stem cells or bone marrow, visit www.anthonynolan.org or www.dkms.org.uk. To give blood, visit www.nibts.hscni.net.