The back stories of the Cahills: Amy & Dan

Amy & Dan were 7 & 4 when a fire destroyed their homes. Seven years later, their only other kind family member, Grace dies from cancer and leaves some certain family members an option between 1,000,000 dollars or a clue in a incredible prize. Taking the clue, they soon realize that their parents were murdered and that they were part of a branch and there was more evil other than their own family.