Grief is a natural response to loss. It has no set pattern and everyone experiences grief differently. Children and adults grieve differently due to their developmental stage. This can prove difficult for parents to understand and cope with.
Young children can struggle to understand the permanency of the loss and can express grief through tantrums or regressive behaviour. Teens on the other hand may not know how to express their grief and will need some space to process their loss. Some may choose to grieve alone as they don't want to stand out or be seen as not coping. Whilst others who have a greater understanding, may start to question their own mortality.
There is no specific time frame in dealing with grief, it is up to the individual. For some it can take weeks and months, while for others their grief can last for years.