I don't own Harry Potter, Avengers, or Charmed!
Harry Potter was only a year old when his father disappeared from his life, and his mother sent him to live with her sister and brother in law, not that he remembered either of his parents. He wasn't with his aunt and uncle long before they realized his mother wasn't going to return for him, and quickly turned him into the family slave, beating or starving him for any imagined slight. They took great pleasure in reminding him that his parents hadn't wanted him, that they had abandoned him, laughing at him when they over heard him praying for someone to come take him away late one night. The beatings were at their worst when something unexplainable would happen around him, he would swear that it wasn't him, but they would never believe him.
Little did five year old Harry know his life was about to change.
"Where is the boy Petunia?" Severus Snape asked his sister in law as he stood on the front porch of her home, intent on leaving when the little child his wife had brought here so many years ago. He had been under the impression the child had been killed, that was what Lily had told him. She had said that Harry had managed to get out of the house while she was cleaning up his sister Dahlia, and had drowned in the lake on the property. He had found her attitude when she was telling him about the accident odd as her husband had disappeared on a mission just a few months before the accident, but Lily hadn't been overly upset about either one. At first he had just thought she was in shock, then she'd told him she loved him and wanted the two of them to have a life together on Potter's dime, and suddenly he realized he had the perfect way to get back at his childhood bully.
So he married the woman of his dreams, and raised his school enemy's daughter as his own in the man's own home, and while he didn't touch the man's money, he didn't stop Lily from spending it either. That had all changed a month ago when he found Potter's diary in the manor he and his family were living in. Apparently Lily had cheated on Potter, which was not a shock to him as he was the one she cheated with. What was a shock however was that she had ended up pregnant as a result of the affair and had tried to pass the baby off as James. He had remembered asking her if their was any chance that the child was his and not James's, and she had told him that it would be impossible as she had use a charm to prevent it as she was trying to get pregnant with James's heir. What she didn't know was that while they were sharing a night of passion James was fighting with deatheaters and was hit with an unknown curse.
He read about how over the moon his childhood tormentor was at the thought of being a father, only to do the math and realize there was no way the baby could be his as he'd been gone on a two week mission at the time she would have conceived. To make matters worse, he'd found out a couple of days later that the curse he was hit with had left him unable to get someone pregnant. However, the curse had a loophole for bearers, it would allow them to carry one child. It had been used in olden days as a way of trapping a bearer in an unwanted marriage, it made it so the bearer could only ever have one child, and as said child would be the heir to the sire the bearer had no choice but to stay with their spouse if they wanted to be with their child. Apparently Potter thought that wasn't possible as there hadn't been a bearer in the Potter line in at least ten generations.
Potter had been devastated to realize his wife had cheated on him and that he would never father a child of his own, so decided to drown his sorrows at a bar in London. He woke the following morning in bed, naked, with a complete stranger. He'd tried to sneak out, but the man woke up and seduced him back into the bed, and the two went a few more rounds before Potter finally left, sore but satisfied, and with the stranger's business card.
The morning sickness started a little over a month later, but it was obvious by his writing that Potter was over the moon with the news of his child. The man came clean to his wife, and while she was angry at first, eventually she convinced him that she forgave him, and that they would raise the children as siblings. Seven months later the two went into labor the same day and the "twins" were born. Everyone just thought little Harry was just born sickly, not that he'd been almost a month premature.
James went on to describe the first year of both his son's and Severus's own daughter's lives, and for once Severus felt appreciation for his old nemesis. James Potter had really loved his daughter, and treated her as though she were his own. The man didn't treat Harry any differently than Dahlia, even though the boy was the man's blood and heir. No, he'd treasured both children. It was that reason Severus had been so devastated to realize what his wife had done to the man's son once he'd disappeared.
He knew he could never pay the man back for loving his daughter as though she were his own, but he could start by making sure the man's son was returned to his other biological father. He was just glad Potter had hidden the man's business card in the diary. He was just lucky that, as Harry's father, the man was allowed to know about the wizarding world and magic.
Tony Stark was normally grateful to be pulled out of any business meeting Pepper had forced him to go to, but just this once he found himself wishing he'd been allowed to stay. He tried to keep the fear off his face as he looked at the small child who was sitting on the floor next to the wall of windows in his office, staring out at the New York skyline. To make matters worse, there was no denying his paternity as Tony's own scientists had run the tests, multiple times, all with the same results. "So you're telling me I managed to knock up another man?" He asked the taller man seated in the chair across from his desk.
"That is what I said Mr. Stark." The annoyance was clear on the man's face, as though Tony should believe him just because he'd told the same story the last twelve times he'd been asked the question. "His father was a wizard and a bearer at that, you need to prepare yourself as, while I'm loath to admit it, his father was a powerful wizard, and your son is likely to be the same."
"What do I need to be prepared for, like in the next week or so? I want to have time to wrap my head around the fact that I now have a little person depending on me before I have to wrap my head around magic. I was hoping you could give me an idea of what to expect, then in a week or so I will fly out to where ever you live and you can fill me in on anything else I need to know." He tried to give the man his full attention, but his eyes kept drifting back to the child that hadn't said a word since he'd first laid eyes on him.
"He's young, so unable to control his magic. You can expect that, during moments of extreme emotional distress, he'll have bouts of accidental magic. Small things like stuff levitating, glass shattering, or items shaking." Tony didn't know if he wanted to believe the man, or if he wanted him to be just having a go at him. "There is one thing you need to know..." He was surprised to see the man hesitate, "My wife, she left him with people who know about magic and hate everything to do with it..."
Instantly he felt anger rise up within him, "You think they would have dared to lay a hand on my son?!" He'd never felt anger like he felt at the thought of someone laying a hand on the tiny five year old sitting quietly by the window. "If I find out they were the cause of a scratch I will have them in prison before they can even think...throw enough money in there I'm sure I can make it happen without a pesky trial." He was surprised to see the man react as though he'd just remembered something.
"Now, no offence, but I think I'd have better luck getting to know my son if we had some one on one time." The man gave a slight nod as he stood and turned to leave. Tony wished he'd been surprised when Harry jumped up ready to follow him, "No son, you are staying here with me. I'm your daddy so that means I get to take care of you from now on. I have a big house in Malibu, with a big back yard that you're going to love. I'm gonna build you a big swing set, may a tree house or two. I'm going to have a big penthouse apartment here once my tower is completely built, complete with swimming pool, so I can teach you to swim..." He was so caught up in trying to talk his son into liking him that neither one of them noticed Severus walk out.
"Now, I'm hungry, are you hungry?" He looked into the big green eyes so like his own mothers, and his heart beat a little faster when he noticed the hope shining through them. He was starting to think his son didn't know how to talk, as Severus said he hadn't said a word to him since he'd taken the boy from his aunt and uncle. "How about we go get some lunch, and then you and I can go shopping. I don't have much a five year old would find interesting, and it looks like you could use some new clothes." He'd offered to pay Severus back when the man had let slip that he'd been the one to buy the outfit his son was wearing, but the man had refused. He'd said Tony would have enough to buy since the outfit was about all Harry owned. "So how bout it, are you hungry?"
His heart soared when he heard the tiny voice say, "Yes," though the child refused to look at him.
"He speaks, be still my beating heart." He dramatically put his hand to his chest and pretended to swoon. Even with his head down he could see the slight smile creep onto his son's face. "You got a cute little voice there kid, I hope to hear more of it some day." This time green eyes looked up at him for a second before finding the ground interesting once again. "Ah Pepper, I'd like you to meet your future boss." His grin showed that he was joking.
He and Pepper had tried dating, but decided they were better off as friends, the fact that they both put their work before the other was a good sign that the relationship was doomed from the start. "Well I'd like to say I'm surprised that you have a kid, but I think we all knew it was only a matter of time." She then knelt down in front of Harry, and smiled at the little boy, "I don't know Tony, he's too cute to be yours."
They were both surprised to see tears start to fill the boy's eyes, "But I want you to be my daddy." Harry sniffled, and Pepper looked like she was about to cry.
It was then that Tony realized he had a little bit of instinct when it came to parenting, "Oh, don't worry little man, I am most definitely your daddy." He said as he stooped down and picked the little boy up and held him against his chest, his heart melting when two tiny arms wrapped around his neck. "Now, how about we let Pepper buy us a pizza to make amends for scaring you?"