Shadow Warriors - Nathan B. Dodge

Cal's father is a drunk. Letty's rich parents fight all the time. Tony lived on the streets with his mother until she died. Opi's stepmother wants her huge inheritance. Sasha's foster family is abusive.

Kidnapped by aliens, they must train as the crew of a galactic fighter to combat an enemy that threatens the entire Milky Way.

They hate each other, but even if they don't train well, they will still be sent into battle to die!