Ross gives sister gift of a lifetime
But the MacKenzie family could not have been more proud when eight-year-old Ross joined his big sister on the ward.
Shannon, 13, had twice fought off leukaemia and when she needed the life- saving procedure, her little brother stepped forward to donate his own bone marrow.
That took place in May and the family from Wallyford, East Lothian, have now been told that the transplant has been a success and that Shannon is on the road to recovery.
Mum Lynsey, 36, said: "It was strange having both children in hospital at the same time. We kept running between the two of them.
"Then when Ross had finished he was wheeled down the corridor and asked to stop by Shannon's window so he could wave in at her. That was a really touching moment, one of those times you just think the world of them."
It is hoped Shannon will return to Holy Rood High School in December, having missed around 18 months of schooling.
In the meantime, she is on a heavy course of medication, which even involves taking daily pills to negate the side- effects of other tablets she's taking for her illness.
The family did receive one boost as she was undergoing the transplant - a procedure that she filmed in order to show others what is involved.
A necklace she had made also fetched 3000 at an auction for the Teenage Cancer Trust charity.
"We couldn't believe that. The bidding opened at 25 or something like that, then we kept getting text messages to say it had gone higher and higher," Mrs MacKenzie added.
The family still faces two trips a week to Glasgow's Yorkhill Hospital to monitor her progress, but all the indications are the transplant has been fully successful.
Mrs MacKenzie said Ross was the last hope before appealing to a national register of donors, after she and husband Euan, 42, were found not to be compatible for the donation.
"There was only a one-in-four chance Ross would be a match and we were so relieved when he was," she said.
"It is something he really wanted to do - he just sees it as helping his sister out. They're very close. I'm not even sure if he's aware it saved her life.
"People tell him he was brave and he says he doesn't think he was. He took the whole thing in his stride because it can be difficult for a child when their brother or sister is very ill because that's where all the concern and attention goes.
"Everyone would always ask 'how's Shannon?' not 'how's Ross?' and he spent so much of his time in hospital with us.
"Then when Shannon went through to Yorkhill earlier this year, he had to move in with his grandparents because we were through there all the time.
"He never once complained and that will stand him on good ground for the future."