Al Murray appeared on Good Morning Britain to plea for blood stem cell donors as his six-year-old nephew battles a rare form of leukaemia.
The comedian, 51, said little Finlay is suffering from juvenile myelomonocytic leukemia, which is so rare only 12 children a year in the UK are diagnosed with it.
Finlay has to endure a full week of chemotherapy every three weeks and needs to find a donor by Christmas.
Al urged viewers of the ITV show to sign up to donor register DKMS to help beat blood cancer.
He said: "I can't imagine what his mum and dad are going through. I'm this close to it and I still find it kind of incomprehensible.
"This isn't just about Finlay, either. Even if we don't find a match for Finlay we might find a match for someone, a dozen people, a hundred people.
"This illness, he says I've got a bug in my blood that we need to squash, that's how he sees it. He's only six and I hope people can help us squash the bug in his blood."
Finlay is undergoing chemotherapy at London's Great Ormond Street Hospital.
The family had found two donors who were a match, but sadly they pulled out of the donation a few weeks ago.
Al said signing up to the register takes just a few minutes and anyone between the ages of 17 and 55 can check if they're elligible.
He continued: "I know there's someone out there, there's definitely someone out there who's a match but we need them to register.
"I'm eligible and look at me; I'm 51 and I'm a schlub, I'm the opposite of someone who runs marathons and I'm eligible.
"This couldn't be easier to do and the change you could make, you could give someone another chance and help beat blood cancer."
Just two per cent of the UK population is registered as a blood stem cell donor.
