If the Witness Lied, by Caroline B. Cooney. The Fountain family children have survived unimaginable tragedy; their father a victim of a horrific car accident and the youngest member of the family "blamed." To complicate matters, when expecting Tris, their mother was diagnosed with cancer and elected to forgo treatment in favor of a healthy baby. The family is scattered, Jack with Aunt Cheryl to care for Tris and sisters Smithy and Madison at boarding school and with Godparents. When Aunt Cheryl decides they should participate in a reality television series for closure, the siblings form a tenuous bond to protect Tris and in the process learn about themselves, and the lone witness to their father's accident.
Witness has a significantly disturbed character in Aunt Cheryl, moves along at a quick pace, and features teenage siblings that are surviving to the best of their ability, yet at the same time believably self absorbed. Once the siblings reunite and decide to take action things fall too quickly into place' final scenes are tidy and almost anti-climactic as they confirm the title and premise.