Why do children get sick?It's not fair!

We found out that my nephew has blood cancer when he was only 2 months old and now he is 1,7 years old.He had a transplant last year and he relapsed.And today he was urgently assigned a seven-day course of chemotherapy before the second transplant.And the doctors said that this is the last hope and we have to take the risk, which means that we could lose him. I can't even convey all my pain. I worked all this time just to keep him alive. I refused everything and saved even on food, I worked 24/7 for nothing? Anyway, I hope for the best and believe that everything will be fine and that all these are temporary difficulties and my nephew will live happily ever after.