Lily actually forgave Snape after he had called her a mudblood. They have an affair and later Grace Lily Snape is born.

» I didn't know you had a sister, Potter. «

What if you found out you're getting a new mommy? Maybe you'd be happy-if that's what it takes for your father's happiness, but what if there's a bonus? Not just a new mom... but new brothers too. And not just any brothers-these are hot, handsome, ladies' favorites, and, worst of all, total perverts! Could you survive living under one roof with them?, and what if, slowly but surely, they start uncovering the secret you're desperate to hide? This is the story of a girl who guards a secret that could change everything. Welcome to Our Sister's Secret.