The Expanding Family — Robert Werry

Just a few months after moving to Springdale High from a big city school, fifteen-year-old Nathan Deane reckons that life can't get any better. He and his now inseparable friend, Robbie White, have done so many amazing things together that people have started calling them the Super-Twins. But Nathan's world is about to be turned upside down, and his friendship with Robbie put to the ultimate test. Meanwhile, Robbie will suddenly find that his quiet family life is changing in the most extraordinary way. The Expanding Family is the second book in the Super-Twins series. It follows a further six months in the lives of Robbie and Nathan, two talented, unconventional teenage mavericks, as they deal with issues of growing up and finding their place in the world.