Sabo was born with a tattoo mark across his chest. His parents were suitably horrified. Age difference was not a bother to them, which this happening proved was a part of things, the problem was that the tattoo was familiar and something of their nightmares. It was a symbol, a well known symbol.
It was the mark of the Whitebeard Pirates.
From a young age Sabo was taught to always keep his soulmate tattoo echo covered. It was something to be ashamed over his parents told him. It was something that no one else should see. Keep it secret, keep the embarrassment away. When Sabo ran away he told himself he’d find out why his parents acted that way. He was determined to know.
It wasn’t because he had a obvious soulmate. It wasn’t because his parents and those like them in nobility preferred arranged marriages and tried to pretend the few born with soulmates did not have them. It wasn’t because of the age difference, because many couples he’d known had an elderly man with a very young woman. It was something else- something different, that made his parents cringe and hiss in anger when he went shirtless or didn’t get dressed quickly enough.
Sabo did not find out what it meant until many years later when in a stream with his best friend while they were taking a bath.
Ace was born with a soulmate tattoo echo across his chest that caused his adoptive grandfather much grief and annoyance. He knew right away what it was from. Garp didn’t bother to muffle or censor his discontent about it. He was told, time and time again, that his soulmate was no good and he should avoid everything to do with said soulmate. That, just because they were soulmates, did not mean they had to have anything to do with each other.
He infranced from these words, and later others when he found out his parents and asked that damning question- do you think I should have been born- and got told that was something only he could answer, that he was just as bad as his soulmate was said to be. Because only a monster could be with a monster.. Right?
Then he met Sabo and he was confused and hurt and young. For a long time did not realise the significance of them both having that same tattoo echo. At the time they had- stupidly- thought that it meant that their soulmates were both from the same crew. Garp had gone off on rants about the Whitebeards enough that they both knew who they were- that they knew what their marks meant.
Ace lost Sabo young, he lost him and did not realise what them sharing the same tattoo echo meant until he was fourteen and sitting in Makino’s bar having read a book on soulmates she had grabbed for him. Ace was not in a good place after that. He spent a month locked up and refusing to do anything. He destroyed that book completely, unable to bear the reality that had been shoved upon him.
Ace spent a month coming to terms with the fact that he had two soulmates- a even bigger rarity than having a soulmate at all- and that he had lost the one he found before he even knew what they were to each other.
It was almost cathartic when he went to get the tattoo in memory of Sabo. A bitter part of him was soothed with the idea that, even if he ever met his other soulmate, a part of Sabo would always be with them- and that other soulmate could never take that away or pretend Sabo didn’t exist. In his spare time he would touch that curving marked out S on his arm and think that Sabo would have called him a stupid sap if he knew what Ace had done. He thought about how Sabo would have reacted- with the knowledge Ace now had, over them having another part of a whole that the two of them seemed to make.
He thought of Sabo’s wild laugh and grin, imagined how pleased he’d be to be something his parents would have been even more horrified over- a triad soulmate .
Ace spent a lot of time thinking, of remembering, of wishing for things that would never be. Luffy didn’t understand, but he did miss Sabo. He was Blank, like most people in life were, he missed his brother- not part of his other half. Ace had never met another with a soulmate, or really, another who knew they had a soulmate due to having gained their tattoos. The only one had been Sabo, Sabo who had had the same tattoo echo as himself- Sabo, who was gone.
Ace left Dawn Island at seventeen and determined to make a life for himself that Sabo would be proud to watch over.
Marco spent a long time not knowing he had a soulmate. Years tended to blur together to him. He had long since become satisfied with what he had, with having just his family. Any dating he had tried had ended horribly, so he had given up on finding someone. Then, one day, he woke up to find a mark on his arm that wasn’t there before.
A S CE it read, in capital letters. The S being in a different font than the rest and with a big X throughout it.
Suddenly, Marco had hope.
There was much speculation about the tattoo, but a Whitebeard favourite was that his soulmate had gotten the tattoo while drunk and had misspelled their name and tried to rectify the mistake with another tattoo artist as best possible. Marco had no idea what it meant, all he knew was that his soulmates name was Ace, and that they were likely a man.
It was years of anticipation and a search throughout the entire grand line before Marco met him- Portgas D. Ace.
At first, the other man, teenager , wanted nothing to do with him. Marco didn’t see a reason to hiding their shared tattoos, but the young man spurned him at every turn. Every time he tried to get close to Ace, to learn more about him, Ace would yell and flinch away. It would take a long time, a good few months, before he found out why. It would take until Ace officially became a Whitebeard and began to trust him before he would find out about his other soulmate and what he had lost without knowing- until he found out what the marked out S stood for.
Marco would mourn for something he would never have, but he would also refuse to just give up or spurn what he now had. They still had each other, and yeah, they may never be completely whole without their third, but it was better than nothing. Marco was used to loss. He was used to grabbing onto what he had with both his hands and refusing to let the good go. He was used to making something good out of something horrible.
They healed together. No one in the Whitebeards knew about the secret third that both Marco and Ace spoke in soft and almost reverent tones about when alone. No one in the family realised that the two of them weren’t whole but instead only half put together. The puzzle piece that slotted in along with them was gone, destroyed, and they ached from that loss- but over time the pain became less and more like a cauterised wound created from their flames.
Over time they became happy.