This is just an idea I've had for the last week or so floating around. It does not follow the original timeline. This is mainly just background for the rest of the story. I hope you enjoy!
Katniss Everdeen was only twelve years old when she was thrust into the Hunger Games. She was not surprised, she was only twelve, but her name was in there three times. Not more than the kids older than her, but more than the other girls her age. Katniss was the sole provider for her family, at the age of eight her father had died, leaving a catatonic mother, Katniss, and three year old Primrose. The only saving grace Katniss had was that her father had frequently taken her out in the woods to hunt. Katniss was small, skin and bones, but she knew she needed to win the games in order for her seven year old sister to survive. Katniss could survive and she did. During the 70th Hunger Games, Katniss was able to score an eleven in her training, the highest score ever, and then she used her knowledge of the land, the healing knowledge her mother had given her, her bow, and the snares to get to the top eight. As soon as the top eight were announced, the arena was flooded. Five tributes instantly drowned; Katniss of Twelve, Annie of Four, and Razor of Two kept swimming. Katniss thanked her father and her lucky stars for the lake where she had learned to swim. In the end, Razor was taken out by another wave and took the inconsolable Annie with him. Both drowned after hitting their heads against a cliff. Katniss won by staying afloat the longest. At the age of twelve, Katniss Everdeen became the youngest victor ever, beating Finnick Odair by two years. At the age of twelve, Katniss Everdeen had killed four people, and watched two die in front of her. At the age of twelve, Katniss Everdeen went home to raise her sister.
Five years later, Katniss and Haymitch had only brought one other tribute home. Katniss had become a symbol, unknowingly, to the rebellion. All Katniss wanted was the protect Prim, especially after their mother had left them. Their mother had gone off to marry the newly-divorced baker three years prior. She had finally snapped out of her coma-like state, only to leave her daughters again. Peeta Mellark, her stepbrother was her only tribute to come home from the games and it had been a complete accident. He had no kills and stumbled into victory by camouflaging himself until the mutts had taken out all his opponents. Katniss had always raised Prim but now she really was Prim's mother. The girls could not help but resent the whole stepfamily.
This year was the 75th Hunger Games, the Third Quarter Quell. It was also Prim's first year. Katniss was terrified. Prim and Haymitch were the only family she had left and Haymitch was so drunk that even she could barely understand him half the time. The card was being read tonight of the rules to the games. All Katniss could think was that Prim would be sent in with double the tributes just as Haymitch had done. Instead, Katniss would be going back in. As the only surviving girl tribute of District Twelve, Katniss would go back into the arena to face her biggest fears with either her stepbrother, or the man that had taken over as a father for the half decade.
As it turned out, Peeta Mellark had plans to bring Katniss home and volunteered for Haymitch. The two seventeen year olds would be going back into the games with experienced and crazy killers. Peeta being, without any kills under his belt, didn't really ever stand a chance. He knew this though, and went into the games willing to die for the girl who never noticed him. The 75th Hunger Games was all about fear for Katniss. Fear of leaving her sister abandoned, fear of having to kill again, fear of the nightmares, and the fear that Snow would punish Prim for her own resistance. The games were the worst part of her life, but in the craziest way, it was also the best. The games may have been where she was playing a fatal game of cat and mouse, but they were also where she let her guard down and fell in love. The games were where she met Finnick Odair.