As Long As We're Together by Brianna Peppins

Novah has too much responsibility for a fourteen-year-old. She wouldn't mind it so much if she were the eldest child, but she has two older siblings! Then the night of one of Ariana's soccer games, their parents don't make it back home. A car accident takes their lives, and the seven heartbroken kids are on their own.

Since Ariana has just turned eighteen, she manages to convince a judge to give her custody over all her siblings - but then retreats. Zion begins to act out, falling in with a dangerous crowd, which once again leaves Novah as the default parent. But this time, she knows she can't do it alone.

She'll have to find strength in unlikely places to forgive her sister, bring Zion back into the fold, and fight to keep her family intact.