Quicksilver

Pietro Maximoff isn't known to the world at all at this time. He is a college student in Mass.

Quicksilver on the other hand is a mutant member of the Brotherhood of Mutants.

Background
Born to Erik/Magnus and Madga, I am going to start with the parents first.

Magnus was sent to the concentration camp of Auschwitz at an early age, and was in the camps for nearly four years. In order to be able to survive he joined the Sonderkommando, a squadron composed entirely of Jews which was responsible for carrying bodies from the gas chambers to the crematoria. While in this squadron he was given some extra food, and for the fact that he proved useful was not sent to the crematoria as was the rest of his family. It was during his time here that he met Magda. Magnus did a great deal for aiding others to survive, and I have no doubt that Magda was one of them. (I believe it is X-Men #199 where we learn from some of those he helped to survive what a hero he was in the camps. His will and fire to survive lent strength.)

Just weeks before the Americans over ran the camp, and thus freeing it, Magnus found and took and opportunity to escape. Security had been getting more and more lax as the war wound to an end. Now sixteen, he over whelmed a guard and taking Magda with him, escaped. The two lived little better than animals for about six months. They feared being found by the Nazi and so were sticking to the more wild areas. I believe that they eventually came across a farm stead where they were given aid, and thus the real ability to survive. The two made their way to the Carpathian mountains where they would spend many years.

It was during this time that the two fell in love, were married, and had a daughter by the name of Anya. (Backstory in Classic X-Men #12) Years later they moved to the city of Vinnitsa in the Ukraine, for Magnus had trouble finding work, and the family had to continually move about. After a couple of weeks Magnus was cheated out of his rightful pay by his (slimy) employer. Having the nasty temper that he does, Magnus began to argue with the man for the money. With this anger came the first real stirrings of his power; a couple of the tools nearby floated around, frightening his employer. Because of this fear, a confused Magnus was given the money he had rightfully earned.

After having purchased some food for his family, Magnus returned to the inn where he had left Magda and Anya, only to find it in flames. Thinking nothing of himself, the man was all ready to leap into the flames, but was stopped by the police. Magnus' employer had brought them to arrest Magnus for extortion of money. Protesting that he needed to find his daughter, Magnus restrained and then badly beaten to the point of unconsciousness when he wouldn't comply. Upon waking he found his daughter dead for the inn had been burned to the ground. Out of his rage and pain Magnus let loose with his power the very first time. Lashing out about him mindlessly he killed over a dozen of people. Coming back to himself the man found that only Magda has stayed, although she was very frightened. Magnus tried to go to her, but she was terrified of the fact that he had killed all of those people. Calling him monster the woman fled into the night, leaving Magnus in shock. He was never to see her again.

As for Magda she was sick in her own right, very pregnant, and very nearly didn't survive her trip through the wilderness, but she managed to reach Wundagore mountain some time during the last month of her pregnancy and was found by the cow woman, Bova. Bova (Who was a hybrid between cow and human created by the High Evolutionary)gave the woman refuge and played midwife during the birth. Magda named her two children, but with in days of the birth gave them into the keeping of the cow woman for she was very afraid that Erik would be able to find her. She refused to allow that monster to get his hands on her children, and so fled back into the wilderness to try and ensure that he would follow her and thus remain ignorant of his children.

Not knowing what to do with two children she didn't have the means to raise, Bova gave them to a Robert Frank (AKA the Whizzer) and told them that they were his children. Unfortunately, thing didn't at all work out as Bova wished. Robert's wife had mysteriously died and he blamed it on the newborns, believing that his wife had died in childbirth. Now in a quandary, Bova went to her creator and asked for his aid. What should she do with the children?

The High Evolutionary didn't honestly care what Bova did with the children, and in an attempt to return to his work he told the cowwoman to take care of them herself. And so Bova settled in to raise the twins. She had help of course. The Knights of Wundagore Mountain, other creations of the High Evolutionary, were around to lend their aid. They built Bova a larger, more proper home than her cabin, and took turns caring and teaching the two. For six years their lives were very normal, except for their care takers and where they were living. Sure it was strange, but all in all it was a very normal upbringing.

And then the High Evolutionary paid the twins a little attention. Not directly mind you, but a scan here and there, and he realized some of the potential in Wanda. Fascinated by it, for her power would one day be incredible, he took the twins from Bova. With no mind to how she would feel about this, the High Evolutionary placed the twins in stasis so that he could study them more fully when he wasn't so busy. The problem with this is, he was busy for decades. Literally more than half a century passed while the two slept, all unknowing of what their fate would be. This also left a grieving Bova. For years afterward she begged the High Evolutionary to free the children and return them to her. She loved them as if they were her own. Time after time he denied her, and brushed off her pleas. They had no sway over his decision.

By 1997, for time moves strangely on the mountain, Bova decided to act. When the High Evolutionary was away, Bova freed the twins from their stasis and took them away from the mountain. Before leaving she made sure to have their memories repressed of their time with her. She knew they could never return to the mountain.

So with false histories, Pietro and Wanda were placed with the Maximoffs. A couple down on their luck, who had been wishing for children for years. While it was a bit strange the first year as memories settled, the twins found themselves in a safe and loving environment. This soon included a move to London where their father found more steady work after the death of their foster mother. It was a rough decision for Djanga, to leave behind some of his Romany heritage, but he did it for the children.

And in London the twins grew. Nearly always together when they weren't kept apart by school and chores, they were healthy and happy. Until puberty anyway. In spite of Wanda maturing more quickly due to being a girl it was actually Pietro who's power manifested first. In many ways this was a good thing for it brought everything to a screeching halt for the boy. His world was turned upside down, and suddenly he couldn't even interact with it any more. It was thanks to Wanda that he had the support he needed to get a handle on the speeds he could now move at. Pietro had to relearn how to speak, how to interact with people.. in fact he had to relearn a great many things. It was only thanks to his gift at learning that his father had no idea just what was going on.

No, it wasn't until Wanda's powers manifested that their father learned that his children were mutants. Djanga was a good man, and while it was difficult for all of him, he learned how to get passed this, and to deal with his daughter's new troubles. Pietro remained in school, but Wanda was to stay at home and be schooled there. It was safer for everyone involved.

Pietro didn't enjoy their separation at all. They had always gone to the same school together, and he now had to face it alone. The next few years were unremarkable for the most part, excepting for the stress the twins felt in their hours of separation. They made up for it by spending as much time together outside of school as possible. Pietro excelled at school, but avoided most sports thanks his wanting to spend time with Wanda. This led to some uncomfortable rumors, but there was no truth to them, so he dealt with it as best he could.

An idea of a friend had him joining a dojo however. The martial skills taught him some much needed control in both strength and speed. Not to mention gave him an outlet for that anger he felt in situations he couldn't control. A mixed combination of Judo and Karate, he focused on defense more than anything else, yet of course learned more then that.

Pietro didn't date more than on the rare occasion, and thanks to Wanda. Not that she wanted him to hold off, but that he didn't want to leave her alone. It left the young man no lasting attachments.

He did so well at this studies that he received a full tuition for his first two years of college. The problem was this was in America. Discussing it with Djanga and Wanda, the teen realized that it was the best of his options. His family wasn't remotely wealthy, and this free ride was available only in the States. So things were set in motion.

Djanga surprised the twins with a present in the weeks before Pietro left. He had arranged for Wanda to accompany her brother. Their impending separation had them both at their wits end, for they didn't know how to deal without the other. Wanda too would be able to attend college with her brother. They were thrilled. It meant that Djanga had put himself into great debt, but he didn't care. His children were happy.

Their first few days in America were fun. Settling into Massachusetts, they did a little exploring during some free time and all unknowingly ran into an anti mutant rally. Pietro was stunned almost immediately, leaving an untrained Wanda to defend herself. They could have been badly hurt, or even killed, if it hadn't been for a timely rescue from Magneto. He dropped down from the skies and drove off those humans he didn't outright kill.

Magneto's cost for his rescue was to serve. To join his Brotherhood and fight humans like this. While reluctant, the twins felt they were honor bound to do as he demanded. With that they joined the Brotherhood.

So Pietro attends college while he can, and assists his father when the man calls.

Personality
If there were a word that meant stubborn to the hundredth degree, Pietro would be a prime example of it. Pietro is stubborn to the point where you have to bludgeon him over the head repeatedly to be able to get it thought to him that he might not be right. And then it's never sure that he will believe it. This is another trait he gets from his father, and is it both advantage and disadvantage for on one hand it aids in the defense of anyone who would seek to mentally dominate him, and on the other it helps drive away those who might possibly otherwise be his friends.
 * Intelligence: As much as he wishes otherwise, Pietro is in fact his father's son. While not the sheer genius Magnus is, Pietro is none the less highly intelligent. This really shows in his ability to learn, and then retain, all that information he takes in through reading. Pietro has a quick and agile mind, as well as an excellent memory. His gift is in learning, for he still learns with the ability of a child. If his power hadn't cut him off as badly as it did, he would be far different today, and without a doubt a far better person. He totally lacks his father's gift of invention however.
 * Seemingly Hidden Emotions: No matter how much he would love to be able to deny it, Pietro is very much like his father. And far more than merely in appearance. Magnus is a man of great passion, and even greater drive to fuel those passions. Pietro is different only in that he's not suffered the same losses and become as driven. Pietro feels things very keenly, and his reactions to things are almost always emotional. He's a passionate man beneath that cold exterior. People don't normally see this thanks to his reaction times. Pietro literally has so much time on his hands that when something happens he can react to it, think about it, and calm down, all before anyone else even notices he's done so. To those around Pietro normally seems to never show emotion other than anger and consternation. When really, he's just reacted and covered it up before anyone can notice. This doesn't change the fact that he is a highly emotional being. More often prone to feeling his way through situations than in thinking about them. It gets him in trouble a lot.
 * The Crutch: Pietro, despite the fact that he believes otherwise, needs a great deal of emotional support. He needs to be a part of something greater than himself. To him family is everything and Pietro would willing die for any family member without so much as a second thought. He clings to them far too tightly, and gets possessive of them. Especially his sister, Wanda. She's HIS, damn it. If given the opportunity Pietro would give himself completely to something if it proved to have the slightest possibility of making it so that he wasn't lonely.
 * Temper: Pietro sure has one, that's for sure. Most of this actually comes from his powers. For Pietro the world moves at speeds over a thousand times slower than he does, and so he is forced, far more often than he would ever care to deal with, to have to wait for everything that goes on. He is in all actuality an incredibly patient man, but there are a great many times when it simply gets to be too much for him, and he lashes out in frustration at a world that can never move fast enough to satisfy. A great many things are going to set off his temper and when it happens the man will lash out verbally at the nearest source of annoyance. If this proves not to stop said annoyance than he is more than willing to take things physical.
 * Domineering: Pietro is a terrible bully. He gets it from his father (Surprise, surprise). If he believes something, he is going to badger and bully everyone around him into getting things his way. Now, as things seldom go his way, and people deny him simply for the satisfaction of doing so, so he's frustrated a lot. Don't all of you realize that he's right the vast majority of the time? If you don't he will be the first to tell you so.
 * Patience: If everyone only knew.. People are constantly going on about how impatient Pietro is, and how he needs to learn to slow down a little. Take things all in good time. Sadly none of these people have any idea what they are talking about. Pietro will tell them this too, so don't think otherwise. No matter what people believe he is in fact more patient than anyone else he knows. He simply has to be in order to deal with the world as well as he does. It might not appear he deals with it well, but things could be much, much worse. You try waiting ten minutes for someone to say the word Hello. See how patient you are in dealing with it. In fact Pietro is insanely patient. Mind boggingly patient. He spent far too many years waiting. Waiting, waiting, and waiting. Now that the world moves at normal speed, well, he still finds himself waiting.
 * Superiority Complex: He's smart, he's fast, and he's very much able to handle a great many things. Unfortunately Pietro also knows it. Pietro firmly believes that he is better than the vast majority of the world's population and isn't at all bothered with letting everyone know about it. This annoys a great many people, and it's a wonder that people are patient enough to be able to put up with it. Because of this trait Pietro is doomed to be very much alone - at least until he learns some humility. And the odds of that aren't good now are they?
 * Honorable: Despite all of his faults, (And there are a great many of them) Pietro has a very strong sense of what is right, and an even stronger sense of what is honorable. He apparently can't force other people to live by the means of what he feels is right, so he will simply have to lead by example. Even if it makes him unhappy the man will do his best to be honorable. This means that he will keep his promises and in many cases not even lie.