You are the child of snape, pick a gander. Your father has kept you a secret since birth, Unknowingly, people didn't realize you were related to him. They thought you were a dopple ginger, even when you went to hogwarts. The only person who knew everything was Lord voldemort, he tried exposing the secret of snape. That you were his child, but failed. So had something up his sleeve till the wizding war, snape. Never told you who your mother was. Nor did he ever mention her, it's up to you to decide.