You did not include a link to the article that you mention.  I believe that the link below is the correct link.  I am answering this question with regard to that article.  Although I am somewhat conflicted by this issue, I think that it would be ethically acceptable for parents to act as the family in this story did.  I say this because their reason for having a baby is no worse (and is possibly better) than some people’s reasons for having babies.

In a sense, it seems wrong to have a baby just to use its bone marrow to help its sibling.  Immanuel Kant, the great philosopher, once said that it is wrong to use any human being as a means rather than as an end.  This seems like a classic case of using a human being as a means.  You are making a human being for the purpose of using its marrow to help someone else.  By Kant’s statement of the categorical imperative, this is an improper action.

However, I would argue that people have children for all sorts of “bad” reasons.  People have children simply because they failed to plan well and ended up with unwanted pregnancies.  They have children because they want someone to love them.  They have second or third children because they think it will be better for their existing children to have siblings.  In all of these instances, they are having children for reasons that do not really have to do with the unborn child that they are conceiving.

In the case of the Ayala family, it seems like they did the right thing (if they really lived up to what they said they were going to do).  The link says they were going to have the child, use its marrow, and then raise it and love it for itself.  This seems no less ethical than having a child because you don’t want its sibling to be an only child and then loving that child unconditionally.

I guess I would say that it would be ethical to do this as long as you were going to love the child for itself.  If you were going to treat it only as a donor and then abuse or discard or ignore it, it would be terribly unethical.