Skull hadn't always been Skull.
Before being the loud and attention-seeking stuntman, he had been a hitman. Probably as good as Reborn.
He had been Alexander Black, also known as Nebula.
After being introduced to the Mafia at a young age, Alexander had always show a great ability to adapt. He could get out of every situation, having learnt immediatly how to show people what they wanted to see.
He had made a name for himself quickly, becoming one of the best. Quick, silent and without a Boss or someone to order him around.
He was a Cloud.
And being a Cloud meant he didn't like to be caged. So, when a mission had left him a bit shaken and his client all but demanded to have him as one of his Elements, he snapped and burnt the building to ashes.
That night, riding his motorbike, he decided to take a little 'vacation'. He changed name and occupation, becoming Skull De Mort, The Stuntman.
Two years and a letter came. Skull was summoned to a meeting with I Prescelti Sette.
His insticts were all screaming at him, but he went anyway.
He never really trusted anyone of them, Luce in particolar. She had smiles and cookies were others might had threats or weapons, but he wasn't stupid. He could sense how her Flames were trying to bond, almost forcefully. He never knew how the other hadn't note.
He played the part of the civilian, with already a plan - more like four - to escape once he had discovered the reason of the summonig.
But then the Curse happened.
(Skull - Alexander was a Cloud and he had just been caged and it was all Luce's fault because she knew. It wasn't a surprise that he had to fake the tears the day of her funeral.)
Years passed and Skull had learnt to trust the other Arcobalenos, even started to view them as His.
Then there was the Vongola Tenth Generation and, like his Family, he had seen the potential.
It wasn't a surprise when the kids become His too. Not with the way Tsuna's Flames warmed every place he went or his will to protect those precious to him.
(It wasn't a surprise when the Curse was broken, neither. Skull had already known how those kids could do the impossibile.)
So, yeah, Skull hadn't always been Skull.
But the Arcobaleno - or anyone else - didn't need to know.
.
.
(He had always wondered though, how no one had caught his act, because for all his skills he was still surrounded with the best hitmans of the world. Not that he complained.)