Warning: Sevitus (this means sev is Harry's father), mpreg! Don't like, don't read!
Explaining the pastAs they walked away from number 4, neither man spoke a word. They turned the corner onto Magnolia Crescent, and walked towards the house of Ms Figg, the kind old squib that used to be Harry's babysitter whenever the Dursleys were tired of him. She had a floo connection they could use to get back to Hogwarts. After seeing who was at her door, she immediately let them use her floo.
They flooed straight into Severus' personal chambers, witch he locked immediately to keep prying eyes (mostly Dumbledore's) out of their conversation. Silently, he pointed the boy towards a chair. The boy sat down on it and looked at him expectantly. "Well, you wanted me to hear you out? So shoot already!"
Severus wasn't sure how to begin. Even after all these years, he didn't really know how to explain to his son, that he was, well, his son. But he knew he couldn't stay silent for long. Because than the boy would just decide he didn't want to hear him out anymore.
"I'm not sure how to begin, Harry, I ..."
"Wait a minute," the boy interrupted, "did you just call me by my first name?"
"Yes I did, now do you want to hear this, or not?"
"Okay, okay, I'll keep still"
"Good! Oh Merlin, I haven't even begun to explain, and we're fighting again already."
"Sir, why did you act like that at the Dursleys, like you really cared about me? I just don't understand. There is no reason for you to care. You hate me, just like you hated my dad, and just like you hated Sirius! Why did you tell me you didn't want me to get hurt? I just don't understand!" Harry was once again raging.
"First you need to understand something, Harry. I didn't hate your dad. I disliked him for a while, but I never, ever hated him. Harry, I ... I loved him with all my heart. I was devastated the night he died. And then I learned you survived, and everything changed. My sole purpose was to make sure you would survive the war, even if it meant denying myself that what I had longed for most, what could have made me happy."
"Whoa, rewind, you 'loved' my dad, you denied yourself that what could have made you happy? What do you mean by all that?"
"I loved your dad, and he loved me. Harry, your dad was never married to Lily, and she wasn't your mother. He was married to me, and I carried you inside of me for nine months. We both loved you so very much. And when Voldemort attacked your home, and you survived, I had to make sure you stayed safe. Even if it meant I could never have any friendly contact with you. Even if it meant having you grow up without parents."
By this time Harry was just sitting there. He just looked at his pro- no, his father, mother, whatever, not believing what he had just heard. Or what he was seeing, because by this time Severus Snape, Snarky Potions Git, was crying. This just couldn't be real. It just couldn't be! He knew who his parents were, James and Lily Potter, who had loved each other even while still at Hogwarts. Who had never loved anyone besides each other?
"No, no, no, no, no, it can't be! YOU'RE LYING TO ME! QUIT LYING TO ME! YOU THINK IT'S FUNNY TO MOCK MY PARENTS, DON'T YOU! JUST STOP LYING TO ME!" with those words he just sunk back into the chair, too exhausted to yell more, not wanting to believe what Snape was trying to tell him .
"Harry, I'm sorry, I know you don't want to hear this, but it's the truth! Please believe me! You remember the Whomping Willow incident in my fifth year, well after it your dad and I became friends, and eventually even more. Lily, well let's just say she found out pretty early on. And she agreed to pretend to date James, who was like a brother to her, so my parents wouldn't find out. They would have killed the both of us right away, if they had found out. After we graduated James and I married in secret, while James and Lily held a big fake wedding. Only Sirius knew about the real thing by then. My parents had joined the Dark Lord, and they forced me to get the mark too. Don't ask me how, 'cause I won't tell you.
Harry, when I found out I was pregnant, it was the happiest day of my life. I managed to keep the pregnancy hidden, while Lily pretended that she was pregnant. And then I delivered, and James and Lily took you into hiding because Dumbledore told them about the prophecy. I missed both of you so much, but when James died I knew I couldn't go to Dumbledore to claim you. You would've been in danger, not only from those still loyal to the Dark Lord, but you would've been shunned in the entire wizarding world because you were a Death Eaters' son. I couldn't do that to you. But then you came too Hogwarts, and you looked so much like your dad. I'm sorry I treated you like I did, but I had to keep you away! I had to make you hate me, because I wouldn't have been able to turn you away, to not tell you everything, had we been on friendly terms with each other. I am so sorry Harry! But please, please, give me another chance. Give me a chance to show you a reason to go on! Please Harry, I just need you alive, even if you want nothing more to do with me."
Severus was at a loss for words now. He didn't know how to continue. But he didn't have to, because his son was now on the floor, hugging himself and calling out for his Papa.
"Please Papa, help me, it hurts, it hurts to think of daddy, or aunty Lils, or uncle Paddy. Please Papa, make it stop hurting, make me stop remembering."
Not knowing what else to do, Severus knelt down next to his son, and pulled the broken boy into his arms. The boy immediately clutched unto him, and they just sat there for a long time, just comforting each other, both of them just mourning the loss of their loved ones for the first time.