Who is Jake from Crank and what is their importance?

Jake is Kristina's little brother. Jake is her half brother, the son of Kristina's mother and Scott. Jake was a late in life child and was unexpected. He has taken over Kristina's spot as the baby in the family. Kristina refers to Jake as being spoiled. It is Jake who talks to Adam the first time Adam calls Kristina's home. Jake tells Kristina that Adam first asked for Bree. He asks her who Bree is. When Kristina is grounded and forced to pull weeds as a punishment, she convinces Jake to help her. Generally, Kristina's attitude toward Jake is that he is a pest who asks too many questions.