Batman's origin story involving the murder of Thomas Wayne and Martha Wayne has been retconned several times. It was originally established that the mugger had been named Joe Chill and Bruce was aware of this. Zero Hour changed this so that his identity was never revealed, symbolically strengthening the potential link between any criminal and the man who killed his parents. Infinite Crisis said that it had been Joe Chill and he had been arrested the very same night, making this the current version. This is expanded upon in a later story which showed Batman slowly driving Chill insane with mental torture before causing him to snap and commit suicide with the bullet meant for Bruce as a child.
Kathy Kane (Batwoman): First introduced as a female counterpart for Batman, Batwoman developed into a romantic partner in the Silver Age, where many Imaginary Stories featuring Kathy and Bruce getting married were published. Batwoman's love for Batman was never reciprocated and he only saw her as a good friend. On Earth-Two, Batwoman resigned to live without Batman's love, and in the Earth-One continuity, Kathy Kane was murdered by the League of Assassins. In the New Earth continuity, Kathy Kane was romantically interested in Batman in a couple of stories by Grant Morrison, who liked to use Silver Age content as reference in his works.
In the current Prime Earth continuity, Julie is an artist and her father is Mallory Madison, an arms dealer who sold the gun that was used to kill Bruce's parents. Julie first dated Bruce Wayne during their teenage years, but met him again after his mind had been erased and he had forgotten ever being Batman. The two fell passionately in love, with Bruce being prepared to settle down and marry Julie. However, things got so bad in Gotham that Alfred realized Batman was needed and he and Julie were forced to give Bruce his old memories back, erasing his mind of the relationship.
In early 1939, the success of Superman in Action Comics prompted editors at National Comics Publications (the future DC Comics) to request more superheroes for its titles. In response, Bob Kane created "the Bat-Man". Collaborator Bill Finger recalled that "Kane had an idea for a character called 'Batman,' and he'd like me to see the drawings. I went over to Kane's, and he had drawn a character who looked very much like Superman with kind of ... reddish tights, I believe, with boots ... no gloves, no gauntlets ... with a small domino mask, swinging on a rope. He had two stiff wings that were sticking out, looking like bat wings. And under it was a big sign ... BATMAN". The bat-wing-like cape was suggested by Bob Kane, inspired as a child by Leonardo Da Vinci's sketch of an ornithopter flying device.
Batman is an expert in interrogation techniques and his intimidating and frightening appearance alone is often all that is needed in getting information from suspects. Despite having the potential to harm his enemies, Batman's most defining characteristic is his strong commitment to justice and his reluctance to take a life. This unyielding moral rectitude has earned him the respect of several heroes in the DC Universe, most notably that of Superman and Wonder Woman.
In 1994, Bruce Wayne took back the Batman mantle from Jean-Paul Valley. Once he did that, he promptly took a vacation and let Dick Grayson fill in for a little while. When Bruce returned, he was ready along with a new costume that he debuted in a four-part storyline across the four "in-continuity" "Batman" titles of the time ("Batman," "Detective Comics," "Shadow of the Bat" and "Robin") called "Troika" (where they fought some Russian villains). The weirdest part of this costume was that it was not even finished by the time the storyline began!
In a paleolithic Gotham, a primitive tribe simply known as The Deer people encounters a shirtless amnesiac Bruce Wayne equipped with his utility belt in his hand emerging surrounded by a swarm of bats from the cave where Anthro recently died. The tribe of the Deer people mistakenly believe Bruce to be a Bat God dubbed him as The Man of Bats after discovering a set of markings featuring the insignia of Batman, Superman and Wonder Woman inscribed on the cave wall next to the body of Anthro. Bruce, still uncertain of where he is, takes notice of a somewhat familiar crashed rocket ship upon investigating he discovers the contents: Superman's cape (the only thing left intact), a destroyed bat signal, and a shredded copy of the Daily Planet which was launched by the Daily Planet staff prior to the use of the Miracle Machine.
Over the course of the first few Batman strips elements were added to the character and the artistic depiction of Batman evolved. Kane noted that within six issues he drew the character's jawline more pronounced, and lengthened the ears on the costume. "About a year later he was almost the full figure, my mature Batman", Kane said. Batman's characteristic utility belt was introduced in Detective Comics #29 (July 1939), followed by the boomerang-like batarang and the first bat-themed vehicle, the Batplane, in #31 (Sept. 1939). The character's origin was revealed in #33 (Nov. 1939), unfolding in a two-page story that establishes the brooding persona of Batman, a character driven by the death of his parents. Written by Finger, it depicts a young Bruce Wayne witnessing his parents' murder at the hands of a mugger. Days later, at their grave, the child vows that "by the spirits of my parents [I will] avenge their deaths by spending the rest of my life warring on all criminals".
@Krunchyman - You do have a very good point. Also, add on the fact that Batman lost both of his parents at a very young age, and it affected him greatly. Parent or not, I'm sure that there are a lot of people who have lost someone very close to them, and that makes them able to relate to Bruce Wayne's tragedy. Going off of what you said about Superman, has he ever lost someone that was close to him? No, I don't think so.
One day I called Bill and said, 'I have a new character called the Bat-Man and I've made some crude, elementary sketches I'd like you to look at.' He came over and I showed him the drawings. At the time, I only had a small domino mask, like the one Robin later wore, on Batman's face. Bill said, 'Why not make him look more like a bat and put a hood on him, and take the eyeballs out and just put slits for eyes to make him look more mysterious?' At this point, the Bat-Man wore a red union suit; the wings, trunks, and mask were black. I thought that red and black would be a good combination. Bill said that the costume was too bright: 'Color it dark grey to make it look more ominous.' The cape looked like two stiff bat wings attached to his arms. As Bill and I talked, we realized that these wings would get cumbersome when Bat-Man was in action and changed them into a cape, scalloped to look like bat wings when he was fighting or swinging down on a rope. Also, he didn't have any gloves on, and we added them so that he wouldn't leave fingerprints.