Percy was born to muggle parents. His accidental magic began showing up around 8 years old. Soon after that he met "Uncle Winston". He was somehow related to Dad although his explanation was rather fuzzy. Uncle Winston was Percy's family's introduction to the Wizarding World. It wasn't much of an introduction, that had been the only time they had seen Uncle Winston. The next news they had from him was soon after Percy turned 10 and Uncle Winston had bequeathed Percy his fortune on one condition. Percy, being the only wizard remaining in the family line, must work to restore the Waterford name to it's previous glory.
His family had no idea how to go about doing this, or if they should. The people working on executing Winston's will recruited Jhonice Treaver, a girl from a respectable family to tutor him in all things a proper wizard should know. Being a student at Sonora herself, she would be able to assist him there as well. And so it happened. Percy and his family moved into the ancestral home of the Waterfords and learned all they could until Percy got his letter to attend Sonora Academy.