Character creation starts when a mommy npc and a daddy npc fall in love.
No seriously odds are two people did the horizontal mambo resulting in your character in your game world. Generating characters while having sex is problematical. But character origins are not often addressed in game (hey, have one of your party's long lost father or mother show up some time for a surprise.)
As Joseph Campbell pointed out in his dissection of mythology, heroes (villains too I guess) are different from everyone else. One of the easiest and most dramatic ways to show this from the start is to give him a screwed up family. For example you're hard pressed to find a superhero with live biological parents. Batman lost his parents and became Batman. Superman lost his entire planet to become the Last Son of Krypton (More news on the Krypton cataclysm: the death toll continues to drop.) Losing their family can set the character on a certain path. Losing your species can make you unique (until that annoying cousin of yours shows up.) It could also make marrying and having kids a goal to continue your name, bloodline or species.
Instead of being last of their family/line/planet a character can be the first of his kind! Maybe his parents were a pile of laboratory glassware. Maybe they were compatible species (bloody unlikely in any sort of setting with biology that works the way we understand it.) For an eerie twist a character could be a changeling, a member of another species that replaced a human baby (and when that human shows up look out.)
Or you can be the second of your kind, a clone (or third or fourth or whatever.) I mentioned a group of clones as the basis for an adventuring party in an earlier post. Finally a character could be synthetic or magical in nature and blissfully unaware that their parent is actually their maker. They could be told they have a grand destiny that is more a matter of being built for a certain job.
Missing parents are often the prelude to unusual upbringing. Tarzan lost his parents and was raised by apes. Cat-Man was taken in by a kindly tigress (who fortunately thought he must taste awful.) Romulus and Remus were raised by a she wolf. All went on to lucrative careers as Lords, mystery men and empire builders. SF also has a fair share of stories about children raised in virtual reality to become spoiled, bratty psionics or what have you.
Odds and Ends
Finally even having your parents may not be enough to save you from an origin. Check their history to find any evidence of radiation, chemical, biological exposure, family curses or blessings, fae blood, or ghostly relations playing guardian.
Closely related to birth is the superhero origin. In the case of mutants the two are intertwined. Mutants were originally devised so Stan Lee and Jack Kirby could take a weekend off, I'm sure of it. Making up new origins is hard! Oddly very few super hero rpgs start play with an origin despite origin issues being the most sought after comics. You might want to start a campaign with all the characters receiving their powers, possibly from the same source (it worked for the Fantastic Four and X-Men.)