Charlie Craig has been diagnosed with myeloid leukaemia and desperately needs a bone marrow transplant to help him battle the aggressive cancer.Last year doctors thought he had overcome the worst and was in remission, but six months ago the family was dealt a devastating blow that the cancer had returned.His search for a potential donor, doctors have said, has been made all the more difficult because he has a rare tissue type and efforts to find a match within the family have proved unsuccessful.Charlie's mum Cliodhna and dad Fintan are urging people to register to be a donor.Cliodhna said: "It was a huge shock to hear it had come back."I just thought it had gone, it wouldn't be coming back and life for us was back to normal."But I am sure a donor will be found, I just know it."Charlie has such a zest for life, there is so much spirit in him."When he was in the middle of treatment last year he was laughing and giggling away."The doctors said this will be the fight of his life and we know he will give it a good go.Cliodhna CraigShe added: "It doesn't take much to register. It's a matter of filling out a form online and sending off a spit sample."Only when someone goes to find a possible donor will you be contacted and in around 80% cases it's as easy to donate as it is to give blood."In only a small amount of cases does a donor have to go under general anaesthetic and have it extracted from their pelvis."Fintan added: "We'll keep fighting for Charlie. He is a great character with real fight and we know that's what he wants to do."We would urge as many people as possible to register to become a donor because there are many others like us out there that need the help."On Saturday, 22 March between 10am and 4pm a donor recruitment drive will take place in Cookstown in Holy Trinity College and in Whitla Hall, Methodist College, Belfast.