KATARINA 'KATYA' MAXIMOFF was born in Sokovia two years after her older siblings Wanda and Pietro, twins. Although she grew up relatively poor in the war-stricken country, she was always grateful that she was able to have both of her siblings as well as both of her parents.
Each Maximoff sibling was way different than the other. Wanda was observant and anti-social while Pietro was hyperactive and mischievous. Katya had always been a people pleaser. She was charismatic as well as naive in the sense that she always saw the best in people.
Each sibling balanced the other out, their parents saw them as their little miracles, the only brightness that they got to experience after a rather long day trying to work as much as possible in order to put food on the table and pay the bills.
Katya was only eight years old when she lost her parents, the twins had been ten years old. Their parents had finally gotten a night off from work so they could all have a family dinner, all five of them. It was supposed to be a happy night for them, however, it turned deadly real quick.
A mortar shell hit their apartment building and killed their parents instantly, making a huge hole in the floor where their parents' bodies had fallen into. Pietro had pulled his sisters under their shared bed(due to the fact that they were poor and lived in a studio apartment) right before the second shell came crashing through the apartment and landed three feet away from them in the rubble.
The three siblings waited two excruciating days for the shell to finally explode but it never did. During those two days they all practically studied the English words on the side of the shell. Although their English was rusty, "Stark" was printed on it clearly.
After they were rescued, the three fell into the cracks of Sokovia's barely functioning foster care system due to the war and poverty. They stayed with a nice older woman named Petra until she passed away.
The three siblings were apart of the protests against the foreign forces trying to invade their country, protests that were secretly orchestrated by HYDRA themselves as a distraction from their experimentation.
Their passion and strength made them get on HYDRA's radar as potential experiments. They were told that they would be given the power needed to drive the foreigners out of their home country, making them agree instantly.
Out of all the test subjects, only the three Maximoff's survived which baffled all of HYDRA's doctors and scientists. They were especially taken back when Katya had survived despite being extremely young.
It also seemed that their newfound powers were connected to their personality. Katya was able to siphon energy and elements from the earth and bend it to her will, using it to either hurt or help others.
They were HYDRA's, and Strucker's specifically, most special weapons on a much different level than any super-soldier would be. They were kept secret as much as possible until the Avengers raised their Sokovian base and the three decided to fight back.
They were later approached by a rogue AI created by Tony Stark himself, one that defied its creator, named Ultron who wanted to end the Avengers with the help of Wanda, Pietro, and Katya. He made them believe they were doing the right thing, but they soon learned that their own personal hatred clouded their judgment and was on the wrong side of this battle.