Summary: The day Alec made his discovery was both the best day of his life... and the worst.
He'd noticed something off long before he knew the truth. the way he saw things, the way he balked at the way his parents treated others, treated Izzy and Jace even.
He'd shrugged it away, figured it must have just been another Shadowhunter's influence, something he'd seen and liked, something that just resounded in him like being kind to Downworlders, even when they had broken the Laws, smiling at children, softening his shoulders to seem less of a threat to them especially little Warlocks who had likely never been treated kindly by his kind.
He never really thought about it much, never thought about how he wasn't like his sister, just the way she moved was different and he'd thought, perhaps that it was influenced by her being a girl, he wasn't sure.
The shift in perspective had happened when he'd arrived to help Magnus Bane heal Luke Garroway. When Alec had offered everything Magnus needed, they'd opened a door of some sorts, a portal if Alec dared to use the term, that passed power between them, it only happened when trust existed between people, it was a trust that should only exist between Parabatai, or so Alec had always been told.
But there had been something beyond Magnus, Alec's own Angelic power had reached and sought it, had wanted to help. It was something he'd never heard about and being both worried and curious had snuck into the Libraries to find his answers. What he discovered was a book centuries old that spoke about familial lines and Runes made by people who shared the same bloodlines worked better than if a stranger Nephilim made them.
He'd asked Izzy, had experimented with it with her, she trusted him but he had discovered that the feeling of his Angelic Powers transferring was different, even with Max, it had been easier to feel his powers flowing into Luke through Magnus and he didn't know what it meant, didn't understand but he let his search and the mysteries fall away because he had more important things to do.
It scared him, what it might mean.
It was after everything had settled down that Alec picked his little project up again, went searching through the books to find what he needed, a Rune that would map a Nephilim's lineage, it was meant for Orphans Alec supposed, to find them family and home.
He lay the Rune out on the page he'd found in his blood as the instructions demanded and watched his blood sink into the page and then flow up and form his own name at the very bottom, a line stretching upward to connect his name to his mother, Maryse Lightwood and he held his breath as he watched the first line of his Father's name become, not an R but an L and Alec knew, he knew with a suddenness that had him sitting heavily on the ground, trying to catch his breath.
Robert Lightwood, the man who had raised him, who had terrified him as a child, was not his biological Father, not that he had been much an adoptive one, he'd refused to speak on e word to Alec since Alec had shut down his comparison of him and Magnus to Robert's own affair.
Alec took a moment to breath and then climbed to his feet to look at the paper again, wondering if he himself had been the result of an affair. But as he compared the dates of his birth, his parents' marriage and his father's turning, his betrayal by Valentine Alec discovered that his mother had been pregnant when she'd married Robert Lightwood.
Alec had always been told he'd been early, but he'd never shown any sings of it in his life, not even when he'd first been born at almost ten pounds and twenty three inches, he'd been large for a preemie, too large for it to be truth. Maybe that had been it, the thing that made Alec wonder subconsciously.
Izzy and Max only being half related to him explained why his Angelic power was reluctant to respond, but the way it had responded to Luke, as though it recognized half of it's origin.
The question was what should Alec do with the information? Maryse had obviously never meant to tell either of them, for whatever reason, whether to protect herself or Alec, Alec didn't know. But should Alec tell her he'd found out, should he tell Luke or just let Maryse's secret remain so, a secret kept by two.
What purpose was there to tell Luke that Alec was his son anyway? Luke was building a new relationship with Maryse or perhaps Alec should say renewing their old relationship. If Alec told Luke, told Maryse then he could break the fragile relationship they were trying to build.
Alec stared at the paper that was still listing ancestors and made a decision he lifted the paper in his hand and his Stele in the other and made the heat Rune and watched his ancestry burn, he'd keep the secret his mother had created by...
Alec's breath hitched a little, the secret she had created when she'd made the choice to keep him instead of getting ride of him, kept him to be born instead of killing him before any one but her had known he even existed.
It would have, could have, been easy for her to get rid of him, know one but herself would have been aware that she had, he'd have just been a small regret perhaps, just another life she'd taken, another life lost in Valentine's War, a life that only one person would know had even existed.
Alec sat at the table in the library and he wondered why she hadn't gotten rid of him, it would have been better for her, she wouldn't have to lie and there would have been nothing to discover, nothing that would ever implicate that Maryse Lightwood should have given birth to an child older than Izzy.
And Alec wouldn't have existed, he'd have never met Magnus, Magnus would never have known him, would that have made things better or worse, Alec wondered.
But she hadn't gotten rid of him, she'd kept him, probably lived in fear of someone doing the math and coming out with the truth, that it was impossible for Alec to have been premature, that he wasn't Robert Lightwood's child that he was technically Bastard born, his parents unwed to one another, she had risked destroying her worth among the Clave and her fellow Shadowhunters to keep him, to bring him into the world, the piece of the man she loved that she had helped create.
Alec wondered if he might have been brave enough for that if he'd been born a woman, if Magnus wasn't a Warlock and sterile. Would he have risked everything to bring Magnus' child into a world that hate him if the truth was discovered?
Alec paused and thought about it, thought about how Luke had been lost to Maryse, a werewolf now and thus no longer welcome in their community, how they would have had nothing if she had gone with him, it would have been so easy for him to have been lost due to lack of nutrition or other factors, even if Maryse had gone with Luke she'd have raised a deRuning and he'd have been dead for sure if she'd undergone a deRuning while pregnant.
Alec took a breath and let it out, he understood his mother's choice, understood and accepted it, maybe she hadn't realized what would happen if she'd gone with Luke, maybe her reason's for staying had been selfish or rooted in Valentine's ideals, Alec didn't know but he was glad for it because it meant he'd been born, it meant that he'd been born, that he'd met Magnus and so many others and how easily one choice might have changed all of that.
And Alec knew that, he knew in the same way that he'd known there was a connection between him and Luke that day when he had put his hand and his power in Magnus' hands, that he would have done the same thing.
He'd have lied and kept secrets if it meant that he'd bring Magnus' child into the world safely. Alec supposed he was lucky then that he'd never have to make such a desicion.
Alec looked at the ashes he'd created by burning his ancestry paper.
He'd keep his mother's secret, he'd carry it to his grave if he had to because without it he might have already been in one.
A/N: Realized that I didn't really explain why it was both the best and the worst day. It was the best day because Robert wasn't his father and the worst because Alec could never tell Luke that he was his son.