There were originally 4 McCafferty books - one for each sibling. They were combined into 2 books with 2 siblings covered in each. In the first book, Thorne, the half sister Randi is in a car accident. From what I've read, that mystery continues through all 4 books, so no solution should be expected in a hurry. It semes like someone may be trying to kill all the McCaffertys, but are they or is the family suddenly accident prone - or stupid, doing things like flying in a show storm?
Someone does try to kill Randi while she is still in the coma so it seems like someone is out to get her at least. Randi finally wakes up after a month in a coma in the book where Matt is the seond book about Matt.
In the first book, Thorne gets together with Nicole who he had a relationship with 17 years earlier. She is a divorcee with two twin girls.
In the second book, Matt gets involved with Kelly who is investigating the attempts in Randi's life
This book was more on the romance side rather than the mystery or suspense.