“Saviour Siblings” vs “"Whoops I did it again" Kids: Any Ethical Difference?

From BBC News, here is story of what a family in Minnesota did in 2000 to save their daughter from a fatal illness.

"A test-tube baby has been selected by doctors using controversial genetic screening to save the life of its older sister.
Already questions are being raised about whether the baby boy was really wanted or merely 'created as a medical commodity' to save his sister.
Doctors genetically tested the embryos of an American couple before implanting one of them in the mother's womb.
They chose the embryo that would have the exact type of cells needed to save the couple's six-year-old daughter, who is suffering from a life-threatening bone marrow deficiency."

Stem cells were taken from the resulting boy to be given to his sister to restore her damaged bone marrow.

A similar case in California in the early 1990s involved a daughter born, after genetic selection to be a bone marrow donor for her leukemic sister. Such children born to donate to their siblings are called “saviour siblings”. There, obviously, is controversy whether it is ethical to analyze a number of parental zygotes, find the appropriate one and then implant it in the uterus, anticipating the birth of a child who can donate cells to their sick sibling. Some wonder if this amounts to bringing only a "commodity" into the world. There is nothing in these stories about ‘saviour siblings” suggesting the new child is ignored or unloved.

An ethicist writing on a bioethics listserv wrote the following recently:

"Personally, I think I would have been a lot nicer to my younger brother
if I'd known he saved my life.

As to the charge that a child conceived and/or selected for this purpose
would be loved less, we don't interfere in parental reproductive
decision-making that is motivated by far worse motives. Nor is there any
evidence that saviour siblings are any less loved. In fact, I suspect
that once we have a sufficient number to study, we will find that these
kids, like the kids of IVF and ARTs in general, have better and more
attentive parent-child relations than the ‘whoops I did it again’ kids."

I wonder what my visitors think about the ethics of this practice and particularly if there should be any concern about the parental love and attention of these “saviour siblings” And what if more than just cells or bone marrow is to be donated but actual organs or parts of organs? . ..Maurice.

ADDENDUM 6-5-2008: After reading this thread, you may want to go to a thread begun on this date which discusses the issue of the adoption of a child to serve as an organ resource.