Disclaimer: This is a multi-category crossover. The story follows the MCU up until Civil War, then diverges for obvious reasons. Agents of SHIELD up until Season 3 and the Netflix shows are also considered part of this fic's timeline. Of the X-men franchise, only I've only embraced the First Class movie into my timeline. Obviously, I don't own any of the characters, etc. etc.

Note 1: This story was first published on AO3 under my pen name SonnyGoten. The story was published as two parts, namely 'All in a song' and 'Broken Chains' of the series "Tony Stark defies Destiny's Will". I decided to post the two parts merged together as one story, but you will notice a certain shift in tone and also an increase in POVs as the story expands dramatically in the 2nd part.

Note 2: Be aware that I came away from the Civil War movie as Team Iron Man and so this story is rather Team Cap-critical. That being said, this is a fix-it fic. Sort of. All members of TeamCap will come to some sort of understanding with Tony at the end of this fic, at the very least; even Steve Rogers (whom I severely dislike at the moment, but I'll do my best not to bash him).

PART 1 : All in a song

Chapter 1: It's so quiet

When Steve Rogers was a small child, he did not understand the people around him who kept talking about the sweet lullaby that was supposedly heard inside their heads. His mother gave him a hesitant look, as he voiced his worries to her.

"Sweetheart," she said, "you're still so young. Perhaps your one and only hasn't yet been born."

His concerns allayed for the moment, he did not think of the matter any longer.

But as he grew up, his head always remained silent. Even when all the children around him one by one got to hear their heartsong, his head remained woefully empty. One day, as he thought back and remembered the worry in his mother's eyes as she tried to comfort him, a sudden thought came to him. What if he would never have a soul mate? What if he — sickly as he was — was never supposed to have one, because he was going to die young and alone?

He was afraid to ask his mother. Afraid to know the truth.

When Steve reached maturity, World War Two broke out.

One day his best friend Bucky came to him, face pale and eyes red.

"I don't hear it anymore," he said hoarsely.

Bucky's heartsong had died out. His soul mate had died before they had ever met.

"I... know how it feels. Not hearing it," said Steve. "I've never heard mine."

It was the first time he told anyone outside of his mother.

That night the two friends commiserated and sought solace from each other's warmth, the sound of their passion breaking through the quiet in their heads.

When the war reached American soil, there was no time to think of soul mates anymore.

During that fateful war many voices died out. But for Steve Rogers, who had taken the serum and become Captain America, then flown himself into the Arctic ice, a new beginning was waiting for him.

TBC...