Notice that the dad--only identified as HU--was no longer with the mother, as he refused to pay child support too. I suspect that letting the boy die was just a convenient way to wound the mother through destroying her child.
Beijing father refuses to donate bone-marrow to 5-year-old son, boy dies
Parenting fail. A five-year-old boy in Beijing has died of complications arising from leukaemia after his father refused to undergo a bone marrow transplant that could have saved the boy's life.
The boy's father, surnamed Hu, was found to be a compatible donor last August and originally agreed to undergo the procedure. However, earlier this year Hu abruptly refused to donate his bone marrow and also stopped paying child support.
Hu did not attend his son's funeral.