Note that the biography below is under construction, so e-mail me if you find any inconsistencies between it and canon Trek.
Kira Taluno was born on Bajor in 2343. His was a childhood more troubled than would be expected of most Bajoran children who suffered the Cardassian occupation: he was separated from his parents by the Cardassians when he was 11, and he never saw them again.
Kira's father, Vedek Falor, had placed a close second in the balloting when Opaka was elected Kai. As a result, Taluno and Jaxa were good friends of the former Vedek Opaka. In fact, Taluno had been named for Kai Taluno, who may have been the first to encounter the Celestial Temple, or the "wormhole" as Starfleet calls it.
In the latter part of the 22nd century, according to Deep Space Nine science officer Jadzia Dax, a ship carrying Kai Taluno was disabled for several days in the Denorios Asteroid Belt. At the time, however, the Denorios Belt was considered a navigational hazard; no one flew anywhere near it unless they had to. And in its disabled state, the ship carrying Kai Taluno wasn't in much of a position to get away from it. There, Kai Taluno had a vision: he said the heavens opened up and nearly swallowed his ship. Dax would later describe him as not being a man prone to exaggeration-- as a diplomatic apprentice at the time, she had been one of his acquaintances.
Kira's mother, Kira Jaxa, had been in the Bajoran military at a time when the Bajoran resistance was at its peak. Kidnapped by surgically altered Cardassian infiltrators in 2354, Jaxa was tortured for information regarding a planned revolt against the Cardassians. During their interrogation, the Cardassians traced her husband and son and brought them to her, threatening to kill them if she did not reveal the location of her military unit's base of operations.
Falor and Taluno escaped the Cardassians' clutches in an attempt to free Jaxa, but they were too cautious. When the Cardassians discovered their latest Bajoran prisoners gone, a massive manhunt was initiated, putting Jaxa one step closer to execution. Falor saw his chance when a Cardassian who was guarding the entrance to Jaxa's inquisition had to be called away to aid in the search. Directing Taluno to hide and wait, Falor went alone to try to free Jaxa.
After waiting a seeming eternity, Taluno sensed this was taking too long and decided to emerge. Immediately he was grabbed from behind by a Cardassian who transferred him to the now-infamous Gallitepp labor camp. From or about his parents, Taluno would hear no more.
Under Gul Darhe'el, the commander of the camp, Kira endured forced labor almost to the point of death, being allowed to pause only to eat or sleep. When Darhe'el was ordered to leave Gallitepp in 2357, he ordered all the Bajoran laborers be executed. Kira survived the horrors of Gul Darhe'el's butchery long enough to see the Shakaar resistance cell break into the prison camp, which freed Kira and all of the few Bajorans who were left. Given his newfound freedom, Kira decided that after having suffered for so long under Cardassian oppression, no one--Bajoran or otherwise--should ever have to suffer again as he had suffered.
An ideal scenario would have had Kira get some form of civilian employment in social or rehabilitation services, but the Cardassian presence provided hardly an ideal environment for such a job. Besides, his age at the time limited the range of work he could do in that area. And given the strong possibility of an impending major collapse in the Bajoran economy, Kira felt that long-term civilian job security would be uncertain at best.
So even though he was only 14 at the time, he joined the Shakaar resistance. Though there was no relation between him and future Deep Space Nine first officer Kira Nerys, the Shakaar cell often had Taluno and Nerys substitute for one another in an effort to confuse the Cardassians, mentioning them only by family name on open channels. As a result, while Taluno was primarily a minor operative running errands for the resistance leaders and Nerys was not, the Cardassians were led to believe just the opposite.
But after ten years with the Shakaar resistance, Taluno felt he could do more for Bajor. So he joined the Bajoran military in 2367 with three goals in mind: first, to help rid Bajor of the Cardassians; second, to help the Bajorans who had been forced to relocate to other planets and moons, and in particular the children, which Kira felt would be the future custodians of Bajor; and third, to help rekindle his people's faith in the idea that Bajor would once again be restored to the beautiful, peaceful state it was in before the Cardassians came.
Throughout this period, Kira maintained contact with Kai Opaka as best as he was able. Shortly after the Cardassians finally withdrew from Bajor in 2369 after all but decimating the planet, Opaka agreed with Kira's sentiment that among the efforts to rebuild Bajor should be an attempt to comfort the children. He suggested distributing stuffed toys to them, and she agreed, formally requesting him to do so. He took her request to the Provisional Government, who gave assent.
Just two days later, Opaka was killed when the Federation runabout Yangtzee Kiang, carrying her, DS9 commanding officer Benjamin Sisko and Kira Nerys, crashed on a moon in the Gamma Quadrant. Although she was resurrected by unusual artificial microbes on that moon, the nature of the microbes prevented her from leaving. Although Taluno took Opaka's departure pretty hard, he hoped that the Prophets would some day allow him to visit that moon. He has had misgivings about Vedek Winn's succession of Opaka as Kai, believing Vedek Bareil would have been a much better choice.
Fortunately, there has not been any resistance to Kira's efforts to help the children since Opaka's departure, not even from Kai Winn despite Kira's misgivings about her. In fact, as a result of his efforts, Kira was promoted to Private in 2372.