Two stepsiblings-to-be narrate this charming, funny and surprisingly touching family story in alternating chapters. Declan, the stronger of the two voices, is a prickly but sensitive metalhead obsessed with masturbation and Internet porn who lost his mom to a car accident at age nine. Neilly—over whom Dec secretly lusts from afar—is a pretty, popular junior who fiercely defends her father's partnership with a man. When Dec's dad and Neilly's mom reveal to their children that they plan to get married, the teens quickly unite in sympathy, forming a refreshingly warm sibling relationship as they come to terms with the changes in their lives. Though the lessons Neilly learns are somewhat pat, Declan's transformation from antisocial lech to tattooed vegan and “boyfriend material” is unique and pitch-perfect, with a satisfyingly realistic number of rejections along the way. Dec's compassionate Aunt Sarah, whose Unitarian Universalist youth group becomes a refuge for both teens, brings yet more wit and kindness to this sweet, emotional, but never hokey mix. (Fiction. 14 & up)