Only a few childhood cancers are hereditary (passed on from parent to child). Parents may feel responsible and blame themselves, even though they could have not prevented the cancer.

You may feel upset and this is completely normal. If you have thoughts or concerns about what may have caused your child's cancer, talk to your medical team. 

In general, the siblings of a child diagnosed with cancer have only a slightly increased risk of developing cancer compared to the normal population. This risk is so small there is no benefit in testing them for cancer. 

Identical twins are the exception in cases of leukaemia. When one identical twin is diagnosed with leukaemia in early childhood, the other identical twin has a 10-25% chance of developing the same type of leukaemia.