When Katniss was 12 (Prim was 8) she got picked for the 68th Hunger Games.  Katniss back then knew how to hunt but wasn't that good.
She got picked along with fifteen year old boy that she didn't know.

The boy and Katniss survived the Bloodbath by running away.
The bow that Katniss could use was taken away by District 9 female tribute.

Katniss climbed trees to hide however one day she was found by the District 2 male.
He first stabbed her leg and then when he was about to kill her, District 9 girl shot an arrow at his head.

The 9 girl's name was Bella and she was 16 years old. She became allies with Katniss and wanted to help her leg.

However, she didn't have medicine.
Then the feast was announced so Bella came there to grab Katniss's medicine.

While she was doing that, Katniss was found by District 1 male and stabbed in the heart.

But on the feast, Bella was attacked by District 2 female but killed her.

Bella cried when she saw dead Katniss and found and killed the guy from 1.

Days passed and a huge tornado went through the arena. Bella survived but the boy from 12 along with 4 other tributes didn't.

In the end, Bella was left with the female tribute from 1.
She managed to kill that girl and Bella won the 68th Hunger Games.

Few years later, Prim and her mum didn't starve because Gale helped them but also Peeta was secretly helping them survive.

On the 74th Hunger Games reaping, Prim got picked along with Peeta.

Peeta joined the careers and then they found Prim.
Peeta was doing his best to convince them not to kill her. So when Clove was about to throw her knife at Prim, Peeta cut her throat from behind and told Prim to run.
The careers then killed Peeta but Prim managed to ran away.

Few days passed and the gamemakers sent a firewall on Primrose. Prim didn't manage to escape and died burned alive.

However that wasn't the end of tragedies in Everdeen's family.

On the 100rd Hunger Games, there was a Quarter Quel. That year only adults were meant to take part.
Then Katniss's and Prim's mum got picked.
She died in the Bloodbath.

When the happen, the whole Everdeen family met in heaven.

They were complete in other world because they couldn't be in the alive one.