Paola-A friend at midnight

This book is kind of sad. Its about a girl who has a step-family. The story starts off when her biological father drops off her real little brother  at the airport just like that telling him he was not the son he had in mind. The girl has to go and rescue her little brother carrying her 23 month old half-brother. Micheal (the abandoned kid at the airport) tells Lily (older sister) not to tell anyone what happened. Lily then hates her father and Micheal stays silent. The Rebeca, the oldest sister, comes and plans a wedding and invites the dad.Right now in the book everyone is questioning what really happened at the airport , why did Micheal come home? The book just keeps getting better and better.