No One Is Alone by Rachel Vincent
Michaela is a junior in high school, living with her single mom. Her dad lives a few towns away and pops in and out of her life only on holidays and birthdays. As a result, they don't really know each other beyond the surface obligations. That is, until her mom dies suddenly, and Michaela has to move in with her Dad . . . who reveals he's been married with kids all this time and she's the product of an affair. Before she can even grieve her mother, Michaela is thrust into a strange house with a stepmom and three half siblings, including new sister Emery, who is less than thrilled at the prospect of sharing her room. Will Michaela be able to let go of everything she's ever known for a family who didn't ask for her in the first place?