Helping Teenagers Cope with Grief
Each year thousands of teenagers experience the death of someone they love. When a parent, sibling, friend or relative dies, teens feel the overwhelming loss of someone who helped shape their fragile self-identities. And these feelings about the death become a part of their lives forever.

Some practical guides to help are shown in this article
http://www.hospicenet.org/html/teenager.html

Children and Grief -

When a family member dies, children react differently from adults. Preschool children usually see death as temporary and reversible, a belief reinforced by cartoon characters who "die" and "come to life" again. Children between five and nine begin to think more like adults about death, yet they still believe it will never happen to them or anyone they know.

Parents should be aware of normal childhood responses to a death in the family, as well as signs when a child is having difficulty coping with grief.

http://www.familymanagement.com/facts/english/children.grief.html