Could you (would you) willingly give your life if you could "undo" the death of the child of a close friend (of your choosing)? It would be as if the death had never taken place, no one to thank, and no memory of your sacrifice...
Before I had children I would have said yes. I now have my own responsibilities.
A sacrifice for anyone like this would be very selfish to your own family. I would only die for my fiance.