When Adam and Eve was driven from the Garden, disease is made part of the human existence. Disease will take the innocent as well as the guilty. The price for the fruit of knowledge is disease, aging and struggle with hunger. Birth will be painful for women. Therefore do not rack your mind with why he was taken. Some of the answers to your questions is in the Old Testament. Not everything in the OT is nullified by the New Testament. Those who make it to Heaven assume a heavenly form or a form with no inequities (no signs of disease and age). Hope this provides some insight to what happen.
Jesus said "Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfill." ~Matthew 5:17
Thank you, Fee. I was going to share something similar. Think not that God took the innocent, but the cancer was the killer. We live in a world where the consequences of sin affect us. Not your nephew’s sin, but humanity’s sin. As a result, we are all recipients of blessings, and at times targets of tragedy.
How we survive, minister, and most difficult, give God the glory through tragedy is where we find the blessing.
Prayers are with you.