Together they can brave the whole world. It has been that way since their parents died in that bombing, when they had been just children. Wanda helps Pietro when everything goes too fast even for him, including his own brain, and Pietro helps her when she doesn't know how she is supposed to behave.
That way they can take on the whole world.
It's a lot harder though, when you take that with suddenly being part of a team that saves the world on a day to day base. Even harder when you started out as their unwilling opponents, and when there is a cultural divide between you and the Americans, one of whom still isn't entirely forgiven for his part in your parents' death.
However, these "Avengers" do their job, and they brought Pietro back from the brink, something that Wanda will never be able to forget, because what is either of them without the other? They help each other deal with the world, and now they have gone from Sokovia, with its civil wars, with the powers vying for its control, with its frequent bombings and the people pressing together in fear, it's still somehow harder than at home.
And both of them know it is because of all the new things that come their way. Neither of them was ever much good with that, and the men who turned out to be Nazis, who convinced two young children that they were good and meant well, not caring for their backgrounds as people they would have killed without a second thought seventy years ago, those same men had noticed that, and has used the difficulties both Wanda and Pietro had to control them.
They had kept them apart to make them more pliable, to make them easier to mold to their ideal of a superior human. They had succeeded, but neither of the two would ever forget the things that had been done to them.
That was one thing that was easier than in Sokovia. People thought them strange enough, called them codependent, but they accepted it, and their strange behaviour, albeit begrudgingly. They did not use it to their advantage, they did not abuse the two strange kids from Sokovia.
The archer, Hawkeye, Clint Barton, the one who had taken them under his wing, who had told Wanda what was what in that ruined building in Sokovia, was the one who minded the least.
The older man shrugged, mumbled something, moving his hands when their parents' indirect killer had asked him why he turned around on "those kids" so quickly. Natasha, who had taken to both of the twins, had explained, in a language all three of them knew.
"He said, "we are the same"." The red headed woman had shrugged, "he's not wrong. We four are the same, in ways."
And observation and the internet had proven it. Though the archer was unknown mostly, and had to be watched to see it, the spy was easier. She too had been an experiment of sorts, taken when she was an impressionable child. But it wasn't just that.
The hawk hid away when things were too much. His earpiece was turned off, and he wouldn't respond, couldn't hear you. The spy dealt with things by mirroring others, at first glance maybe something that was something that had been taught to her, but it was more than that.
And knowing that, that they were the same, the hawk and the spy, it made adapting just a little easier.