One Difference Is All It Takes

We've all read the stories, of a young wizard named Harry Potter. We've grown up or watched as our children grew up with stories of the Boy Who Lived. But what if something was different, what if he hadn't been alone at the Dursley's? What if Harry had a twin, a young girl named Katrina? How would things have been different? Well, you're about to find out. M for future chapters.