Murder
Everyone in his family, narrator and protagonist Ernest Cunningham says, has murdered someone. Some have killed one person; others in his family have killed more than one person. In other words, murder runs in the genes of the Cunninghams. For them, murder is not that big of a deal. They've committed it in the past and they will commit it in the future—unless Ernest stops one of them first. Ernest is shaken to his core by what a murder happened at his family's reunion and wants to bring the person who killed one of his family members to justice once and for all.
Family
The novel's protagonist, Ernest Cunningham, begins Everyone in My Family Has Killed Someone by traveling to a family reunion near a ski resort. Ernest has a strange relationship with his family; he loves most of them but knows that others are complicated or worse, bad people. Still, Ernest goes to the Cunningham family reunion so that he could catch up with everyone. For Ernie and others, family is important. But family is also a liability for Ernie and others after a family member kills someone while they are at the family reunion, something which shocks and angers Ernie.
Trust
Trust is an important theme in Everyone in My Family Has Killed Someone. Ernest Cunningham goes to his family reunion knowing that some members of his family were trustworthy and other members of his family were not. However, after a family member kills someone at the family retreat, Ernest realizes that he cannot trust anyone. To get to the truth of the matter and to find out who killed the person, Ernest recognizes that he can only trust himself. Because at the end of the day, the only person that someone (especially in Ernest's situation) can trust is themselves.
