Cancer is not entirely caused due to hereditary factors. Just the fact that one of the siblings has cancer does not predict that another will have cancer too. Scientists have been able to identify a few genes that indicate an increased risk of some people who have particular types of cancer running in their families, of acquiring the same; but there is no established link.
Your having lost one of your child to blood cancer does not mean that another child you bear has a higher possibility of acquiring the same, or will acquire blood cancer too. You will need to discuss this with your oncologist who could advice you on what is the increase in the possibility, if any, of another child you bear having blood cancer too.