Charlotte Church has urged people to join the Organ Donor Register after revealing the young son of a family friend needs a liver transplant.
The singer and TV chat show host said she was so moved by Finlay Careless's illness she was signing up immediately.
The 20-month-old is the son of her mother Maria's friend Julian, 40, who lives with Finlay's mother Sarah Howell, 33, in Swansea.
She said becoming a mother to baby Ruby had given her a whole new perspective.
Finlay was born with liver disease, and his father approached Mrs Church through his brother Paul, who used to own the Robin Hood pub in Pontcanna, Cardiff, with her and her husband James.
They had wanted the singer to sign a CD for a charity raffle and auction in Swansea in June to raise money for the Children's Liver Disease Foundation.
HOW TO JOIN THE REGISTER
Telephone the Organ Donor Line on 0845 60 60 400
When completing a driving licence application form
When registering with a new doctor or GP'
When applying for a Boots Advantage Card
When applying for a new passport, using the leaflet enclosed with the application form
When registering for a European Health Insurance Card (EHIC), using an enclosed leaflet
Source: UK Transplant
The singer then spoke out publicly about Finlay's plight in a bid to highlight the issue of organ donation.
She said: "I wanted to bring awareness about Finlay. I can't imagine what it's like for a mum to sit and wait [for a transplant]. Finlay has been fine so far but a child could die waiting.
"It's really easy [to sign up for a donor card] and everyone should do it.
"When you think about it, you could save a little innocent child's life - even an adult, who could be someone's dad or sister. It will mean nothing to you.
"Fair enough if you have certain religious beliefs, but if it affected your own family, you would do it without any hesitation. It would mean so much to a family."
Church, who lives in the Vale of Glamorgan with Wales rugby player Gavin Henson and their six-month-old daughter, added: "I'm not registered yet and, in all honesty, I wouldn't have thought to do it if I hadn't heard Finlay's story.
"I'm going to persuade Gav and the rest of my family to sign up too. I'm going to give them all a good talking to."
"As soon as you have children you just realise how precious they are," she said.
"When you become a mother, you become a mother of all, really. All are precious."
Finlay's father Julian said he and his partner Sarah had been grateful for her help.
"If it means one person picks up a donation card or puts a pound in a donation box for liver disease, then it's all going to happen," he said.
John Oliver, from UK Transplant, said: "We're delighted Charlotte is highlighting how we all have the potential to save lives by joining the NHS Organ Donor Register (ODR)," he said.
"Every person who joins the ODR and tells their family is sending a message of hope to the 9,000-plus people currently needing a transplant."