switched at the hospital and organ harvesting

these are the first of many scenarios from my genetics text book.

scenario #1
a family takes their daughter to you, a doctor, to get her blood-typed, among other things. you know that both parents are AB types, and discover the daughter is O, the only phenotype that couldn't be produced from these parents. she isn't adopted, so the only conclusion is that the children were switched at the hospital at birth. the girl's age is not specified, but she's healthy and old enough for them to be classified as a "happy family." do you tell the parents?

i would tell the parents, i would feel obligated as a doctor to be honest. i think the bigger question would be what the parents would do once they learned. the hospital would probably get sued, but would they try to switch the children back? i don't think so, but finding their real child might be a good idea, if only to let the other family know and perhaps swap medical histories. how often do you think that kind of thing happens though...

scenario #2
a young child is diagnosed with leukemia, the treatment for which is a bone-marrow transplant. finding a match for organ and tissue transplants such as this is difficult because of the 3 HLA incompatibility genes, each of which have 20-100 possible alleles. if the HLA genes in the transplanted tissue is not a close enough match to that of the rest of the body's, the body will attack it as a foreign object and it will be rejected. the young child has a rare combination of the 3 genes, and the parents are worried about finding a match in time. they decide to try and conceive a second child in the hope that it will be a match and could donate bone marrow to its sick older sibling. is this ethically right?

in my mind this is a clear and screaming NO. it isn't right to have a child so you can harvest its organs. in addition the procedure compromises the life of the new child, and doing such an operation on someone so young is dangerous. also there is no guarantee the younger sibling will be a match to the older, due to the nature of inheritance it could potentially have completely different alleles for the three HLA genes.