CHARACTERS HISTORY (taken from Wikipedia):

Katniss Everdeen:
Katniss Everdeen is the 16-year-old protagonist of the series. Normally quiet, she lives with her mother and her younger sister Primrose (often shortened to Prim) in District 12, one of the poorest districts of Panem, which is in charge of mining coal for the Capitol. Her looks are typical for someone from the Seam (the slums of District 12): long black hair, which she wears in a single braid down her back; olive skin; and gray eyes. Five years before Katniss became a tribute in The Hunger Games, her father was killed in a mining explosion, and her mother fell into depression. She does not start trusting her mother again until the events of Catching Fire. In order to provide for her family, Katniss began to hunt and pick plants in the woods, just as her father had taught her. In the process, she becomes hunting partners and best friends with Gale Hawthorne, who is also from the Seam and whose father was killed in the same mining accident as Katniss's.
When it comes time to draw the tributes for the 74th annual Hunger Games, Katniss' sister Prim's name is drawn, but Katniss volunteers to take her sister's place. When she is introduced to the Capitol along with the other tributes, her dress is "set on fire" by her stylist, Cinna. This gives her the nickname "the girl on fire", which is used recurrently during the trilogy. During the interviews which precede the Games, Peeta expresses his love for her on live television, which Katniss assumes is a ploy to gain attention from wealthy sponsors. Later, as they grow closer to each other, it appears that his love is genuine, though she is uncertain about her own feelings. Halfway through the Games, a new rule is instituted allowing both tributes from a District to become victors, causing Peeta and Katniss to form an alliance. However, when only Peeta and Katniss are left, the rule is reversed, in an attempt to force one of them to kill the other, which will ensure a more dramatic ending. At that time, Katniss decides that both of them should eat poisonous berries called nightlock, killing themselves and ensuring the Hunger Games have no winner. This is seen by the audience as an act of undying love. As a result, Seneca Crane hastily ends the Games, and both Katniss and Peeta are declared winners, humiliating the Capitol. This choice makes Katniss a symbol of rebellion for all of the Districts.
In the second book, Catching Fire, Katniss becomes aware of her conflicting feelings for both Gale and Peeta. It is revealed that her and Peeta's act of "undying love" that helped them win the previous games was seen as an act of rebellion by the Capitol. Peeta and Katniss compete with each other in the Third Quarter Quell, or the 75th Hunger Games, in which Katniss and several other tributes escape from the arena, while Peeta is captured by the Capitol. Katniss is taken by the rebels to District 13.
In Mockingjay, Katniss helps to end the war, but her sister is killed, Katniss is left burned in a bombing near the President's mansion, believed to be set off by the Capitol, right before the end of the war. After a talk with President Snow, she realizes that it was President Coin of District 13 and the new president of Panem, who ordered the bombing. Instead of executing President Snow, as had been decided, she kills Coin to avenge Prim's death and prevent someone as brutal as Snow taking his place. After being exonerated for Coin's death, Katniss is sent back to District 12. In the epilogue, set fifteen years after the end of the story, it is implied that she has married Peeta, and they have two children, one girl and one boy. In Catching Fire, It is said that her favorite color is green.
Collins has said that Katniss "is a futuristic Theseus."

Haymitch Abernathy:
Haymitch Abernathy is a "paunchy, middle-aged man" who was the victor of the 50th Hunger Games, which occurred 24 years before the beginning of the first book. When he was 16, Haymitch was Reaped for the second Quarter Quell, where four tributes from each district were forced into the arena. He became an ally to a girl named Maysilee Donner, who was the original owner of the mockingjay pin, but later was forced to watch her die. Katniss finds this to be akin to what happened between her and Rue. During the Games, he found his way past a wall of shrubbery to the edge of the arena, where a force field caused anything that hit it to be flung back. When the Games came down to himself (who had been eviscerated) and a female tribute, he positioned himself by the edge so that when the girl threw her weapon at him, the force field sent it back at her, killing her and leaving Haymitch the victor. Within two weeks of his victory, Haymitch's mother, younger brother, and girlfriend were killed by President Snow, as punishment for Haymitch using the force field to his advantage. Since President Snow had left no one close to Haymitch to use to control him, Haymitch instead is "held up as an example" of what happens to those who defy the Capitol.
After winning his games, he became an alcoholic and has spent almost all of the next 24 years intoxicated to the point of embarrassment. Being the only surviving Hunger Games champion from District 12 (one of only two in the history of the games), Haymitch was forced to mentor all of its tributes, which consumed him with guilt by being forced to participate in the games that he hated. He dealt with these feelings by being drunk and openly flouting the dignity of the games. He treats Peeta and Katniss with contempt, and is sarcastic, expending no effort to help them. However, when Katniss confronts him, he is stirred from his stupor and emerges as the pair's greatest advocate and shows himself to be highly canny as he guides his protégés in a cleverly designed, highly unorthodox strategy aimed at ensuring the survival of both tributes.
Although she disliked him greatly at first due to his drinking and his harshness, Katniss later realizes that he is tired of seeing children placed under his care for the Games only to die, and also sees that he cares a lot about Peeta and Katniss. After being in the arena, she realizes that drinking was his form of escape from the nightmares caused by his experiences as a tribute. In the book Catching Fire, it is said that the liquor supply in District 12 has run out, and Haymitch has gone insane, shaking violently and having visions that only he can see (i.e. having delirium tremens). It is left up to Katniss and Peeta to coax him back to health (and get him more liquor). After this incident, Katniss begins to develop a true affection and respect for him. Katniss also realizes that she and Haymitch both think alike, since she was well able to understand what he was trying to communicate to her through the gifts that he sent her in the arena. When Katniss finds out that Haymitch didn't save Peeta at the 75th Hunger Games arena, she claws him and feels that he betrayed her. In Mockingjay, Haymitch is forced to go through detox in District 13 since they do not permit the consumption of alcohol. Despite this, he continues to serve as a mentor to Katniss and Peeta.

I love them both but Katniss is my absolute #1.