After Lilly Potter found out she was pregnant and announced it to those she trusted...which included Snape for some reason. After Snape found out, he was happy for Lilly but was also heartbroken.

So he ended up drinking his sorrows away for a while and ended up sleeping with a woman named Sonia. What he didn't know was, he got her pregnant and she ended up having you...not telling him, because she thought he would be a horrible father.

She never told you about your father, which was weird...but eventually she just said, he never wanted you so you could leave it alone...which hurt your mental health, bc you thought you weren't good enough for him to say and whatnot...so he has no clue you existed and still doesn't know your his kid.

Eventually you went to Hogwarts. You're in your 2nd or 3rd year of Hogwarts. You enjoy the potion class and look up to Snape. Though he is strict about the class.

They had to add a biological class...since well, some parents were complaining because their kids barely knew anything but magic. So they have to add a few new classes.

Your classes are about how cells work, how genetics pass down...just stuff like that...you were somewhat interested in the Genetics part so you can at least know a little bit about what your father looks like...not knowing, they used a spell to show the parents to compare and use as a reference for that.

The new Biology teacher stopped Snape in the hallway and started talking to him, much to Snape's annoyance...after a little while of talking, the new teacher let something slip and everyone around them stopped and stared at them in shock.

???: "I didn't know you had a kid, Snape. I was getting ready for a lesson and I used to spell to make sure everything was ready and I saw they were your kid."

Snape: "...What?"

???: "Yeah, it was pretty shocking...I never thought you would be a family man."