Seeking a bone marrow donor within the family is the first option. A brother or sister is most likely to be a perfect match as a donor. This is called a matched sibling donor transplant. There’s a 1 in 4 chance of the bone marrow cells matching among siblings. One’s parents, own children, and other relatives can sometimes be good matches. Only about 30% of those who need a bone marrow transplant can find a matching donor in their own family.