Giving birth to "savior siblings" - ethical or not?

In the United Kingdom, news of a nine year old girl receiving a life-saving transplant from her younger, specially "designed" brother, is being discussed. Megan Matthews has suffered from Fanconi Anaemia, a condition that can cause bone marrow failure, since birth. Finding a bone marrow donor was extremely hard, and Megan would have died if her little brother, 18 month old Max, did not come to her rescue. Megan's body was unable to produce blood, and needed transfusions every few weeks. Her condition also meant her body was not able to deal with infections in the way most people can, and she would have died without treatment. When a global search for a bone marrow donor that could give Megan some hope did not end successfully, her parents decided to have another baby. The couple, Katie and Andy Matthews, had IVF treatment. They coordinated with medical experts from three British cities to implant embryos that were a perfect match for Megan's tissue so that she could get treatment.

Max, Megan's so-called savior sibling, was born 18 months ago as a result of the Matthews' IVF success. They went through a cord blood banking procedure to preserve stem cells right after his birth, and Max also underwent a bone marrow operation. Max's cells were then successfully transplanted to Megan. The nine year old is now much healthier, and no longer needs biweekly blood transplantation. Of course, it is wonderful that one little girl was apparently cured of her life-threatening illness as a result of the procedure, which was the first successful "savior sibling" in the UK. But what about the ethical implications?

Megan and Max's parents said that they had wanted another baby in any case, and that they were also concerned that any naturally conceived child could suffer from the same condition as Megan. But they didn't hide the fact that Max was, essentially, created to save Megan. As a parent, I more than understand the lengths people are willing to go to to save their child's life. But at the same time, I feel sorry for little Max. Apparently, bone marrow recovery operations result in a lot of pain during the aftermath. And what will he feel like when he finds out he was made to save his sister? What do you think about this? Is creating savior siblings to help heal existing children ethical, or not?