The Pevensies have always been a strong, pureblooded family in the wizarding community of Finchley in London. William Pevensie married the muggleborn girl, and his best friend from Hogwarts, Helen Edwards in 1922, causing a disturbance in the continuity of the community.
Five years later, Peter was born, soon followed by Susan, Edmund, and finally, Lucy. The Pevensies taught their children the fundamentals of magic from day one, and the children grew to love the world that they were exposed to.
It's 1938. Peter is the first to attend Hogwarts. Everything is amazing. The food is amazing. The castle is amazing. This world is amazing. The moment that the Sorting Hat touches his head, it calls out GRYFFINDOR with utterly no doubt. He is welcomed into the lion house and is quite happy with himself. But not everything at Hogwarts is amazing. There he meets a boy that will forever become his enemy: Tom Riddle.
Riddle is a sly child, older than Peter by almost exactly six months, and a Slytherin. A halfblood, like Peter, he detests muggles and muggleborns. This causes problems to rise between he and Peter, problems that will carry on beyond their school years.