I for one think the parents did the right thing. The outcome for both
siblings appears to be a positive thing. There is a trend now to save
embryonic fluid or blood from births just in case it is later needed for reasons like those prompting these parents to have another child.

I know that just last week my Koko was a blood donor for my Sons dog
Desi. Desi would have died around Wednesday, from rat poisoning, if not for Koko being a donor. If saving Desi had been dependent on me finding another donor I would not have hesitated at adopting another dog from rescue. This adoptee would been much loved also. We will usually do anything for our loved ones be it child or pet.