My 9 year old twin daughters were sick and on ventilators in the hospital during their first Christmas. One almost died on Christmas Eve, and the other on New Year's Eve. Santa didn't come to our house until they were both home from the hospital, January 25.
I think we almost go overboard on Christmas now because my husband and I remember what real presents we have, their lives.
I'll say a prayer for your brother-in-law and his family. I'm very sorry for their loss.
Having had a child near death in a hospital at Christmas many years ago, I can empathize. We chose to wait til she came home before celebrating, and now, that she's much older and healthier, it means so much more to us now to have her as our gift from God.