How is family a dominant theme in the novel, Angelfall?

Family is a major and dominant theme in the novel, "Angelfall" by Susan Ee. Thematically family, which includes mutual love or affection, caring, emotional support, and loyalty towards relatives and relations who may or may not be blood related, affects the course of the entire plot of the novel. Family most strongly revolves around the character of Penryn, and indeed, fuels the plot of the entire novel.

Family comes into play immediately. Penryn, who has become the de facto head of her family -her mother and sister- decides that they must head to the hills for their safety. It is love of her family, and desire for their safety, that prompts Penryn to want to relocate. When the escape attempt is disrupted, and her mother disappears, and Paige is kidnapped, Penryn is at once concerned about where her mother is, but even more so concerned about getting her sister back. There is no other singular thought that preoccupies Penryn than the safe return of her sister.

It is love of her sister -of family- that prompts Penryn to force an unsteady alliance with an angel, and to journey to San Francisco to set Paige free. Had Paige not been kidnapped, the plot would have undoubtedly taken another turn that may have had nothing to do with San Francisco. Nevertheless, following the kidnapping, everything Penryn does is to bring her one step closer to rescuing her sister, and ultimately reuniting with her mother.