Posted as my entry for the 20th Anniversary Merlin Fanwork challenge, prompt "Family". Posted here and to AO3.

This takes place a few days before Mordred and Arthur first meet, in terms of canon timeline.

Merlin was tired. It had been a long day. Guinevere was moping over the loss of Lancelot. Perhaps moping was the wrong word. She was sad, she was lonely, but she was also angry. She blamed Merlin – perhaps not entirely wrongly. He had been harsh on her – she was young, intelligent, fierce, and not the kind of person who could live a life devoted to an absent husband who she barely knew. Arthur's knights respected Guinevere, for the most part- she had been their queen and ruler for the last decade. But even they had their suspicions about the nature of the relationship between the queen and her now-absent champion. Lancelot's sudden disappearance didn't do much to dampen their suspicions, it looked too much like guilt. They blamed Merlin, too – and perhaps they weren't wrong either. Merlin had chosen Lancelot as Arthur's champion, after all. Perhaps some of them thought he was reaching too high for a pagan wizard, trying to seek power in Arthur's absence.

Merlin wasn't given to praying – he had seen enough terrible things in his life to struggle to believe in any kind of benevolent unseen god, and the ones he had seen certainly weren't inclined to benevolence, or making Merlin's life in any way easier – but if he was, he would have prayed for Arthur's return. The country needed to remember it's king. Guinevere needed a husband in more than just name. And more than that, Merlin missed his friend.

Pushing open the door of his small house on the outskirts of Camelot, Merlin realised almost immediately that someone had been there in his absence. The scuffs in the dirt of the floor, the books on the shelf that had been placed back carelessly and in the wrong order. The hairs on the back of his neck stood up, in the way that he associated with magic.

"Mab." He spoke through gritted teeth. There was a snort of laughter from the shadows in the corner of the room – a man's laughter. He waved a hand, bathing the room in sudden, brilliant light and illuminating the young man that stood there.

"No, not Mab. Just me, cousin." There was a sneer in the young man's voice. The address threw Merlin for a moment, for he was certain he had never seen this man before, and he knew nothing of any relatives on his birth mother's side. Then it hit him – his hair had grown out, and grown darker, but it was still curled and tinged with a hint of reddish brown, like his mother's. He didn't have magic himself, but he was surrounded by it, power draped around him like a fine cloak – Mab's magic. His "aunt"'s magic.

"Mordred." The man gave a slightly mocking bow.

"Oh, so the great and mighty king's wizard does recognise me after all. Such an honour."

"You've changed a great deal since the last time I saw you." Merlin stared at the young man – he knew that he would grow fast, but he had hoped that there would be more time before he was old enough to come to Camelot, time for Arthur to return, for the kingdom to be more stable.

"Yes," Mordred replied carelessly, "In many ways. My aim is better now." His hand strayed to the knife at his belt. Merlin gestured sharply, and the knife flew out of Mordred's belt and across the room. Mordred watched it go and chuckled slightly, before turning back to Merlin and clapping slowly.

"Oh, very well done." His voice was mocking, Merlin wondered briefly if the boy ever took genuine pleasure in anything, "I'm sure that sort of trick must come in very useful in a court full of Christians – I imagine many of them would prefer to see you dead."

Merlin's arm was still raised, ready to defend himself with magic if need be.

"What is it you want, Mordred?" Surely Mab had not gone to all this trouble to raise Arthur's son and speed his growth only to throw him into some futile attempt to kill her older creation.

Mordred waved his hand, walking over to one of Merlin's chairs and sitting in it, "Oh, I haven't come to kill you, if that's what you're wondering. Auntie Mab doesn't want you dead, cousin, though you have been such a terrible disappointment to her." He lounged back in the chair, putting his feet up on the small table. "No, I just wanted to meet you. I thought it would be fun to catch up, get to know my predecessor. My only real family in Camelot, until father dearest returns."

Merlin stared at him, one eyebrow raised. "Really?" he replied drily. Truth be told, he had only ever thought of Mordred in terms of his relationship to Arthur – the illegitimate son, the source of shame – it had never really occurred to him that Mordred was his family too, in a way. "I'm sorry to tell you this, Mordred, but if you're hoping for family stories I will have to disappoint you. Mab and I have never been close. And since Morgan and Arthur conceived you, I'm not so sure that I would call us cousins, either."

Mordred's mock-friendly expression dropped slightly – but only just. "Come, come now Merlin. Auntie Mab created you. You owe your entire existence to her. She is your mother. And through her magic, she created me too, gave me more than that pair of fools could have alone. Think – she and I are the only family you have left."

"Mab is not my family. Mab destroyed my family." Merlin replied coldly.

"You are a fool," Mordred snapped, "Auntie Mab gave you gifts that anyone with sense would kill for. She would have given you the throne if you'd had the stomach to reach out and take it, instead of crawling around for my father."

Merlin fixed Mordred with a glare, "I've known your father since childhood. He is a good man. A good king. I am proud to serve him."

"Arthur is a weakling," Mordred replied, just as coldly, "He was weak when he slept with my mother. He was weak when he fled the country with his tail between his legs." Merlin stared at Mordred again. He wanted to see something, anything of Arthur in the man before him, of a son that his king could be proud of. But there was nothing – Mordred was handsome, as his father was, but it must have come from either Morgan's side or from Mab's magic, for hardly any of the features were the same. And his smile – that was entirely Mab's, that smirk. Though on Mordred it looked different, less natural, as though he had practised long and hard to match his auntie's smile.

"Arthur is on a quest, Mordred. You may not believe in anything bigger than yourself and Mab's ambitions, but he does. Doing what he believes is right is not fleeing."

"Oh, he was fleeing," Mordred took his feet from the table and leaned his arms on it instead, tilting himself towards Merlin, who was careful to stay out of arm's reach, "He fled with the hounds of hell on his heels – that's what he believes, isn't it? That he committed sins when he lay with my mother – incest, lustfulness, adultery. And of course, he can't actually admit to then, because then that would have left his rule in jeopardy, and his illegitimate, incest-born, pagan son as his one and only heir. But he has to do something to stop his soul burning in the ever-after, doesn't he? So," he gestured widely, "Off he runs on a grand quest, to drink from a cup and gain his god's pleasure. Never mind his kingdom. Never mind his queen. Never mind his son. We have all been left to get along without him."

Merlin stared at Mordred, feeling a small pang of pity for the angry young man across from him. Little though Merlin liked to admit it, Mordred had a point, "I'm sorry, Mordred. Perhaps Arthur did wrong you. Perhaps we both did, for leaving you at Tintagel."

Mordred stared at Merlin as though he was quite stupid, "Oh, dear, cousin – you think I regret my father's abandoning me?" He snorted, "He has nothing I want but his kingdom – and his blood is all I require for that, not his presence in my childhood. I had Auntie Mab – I didn't need your precious Arthur."

"Mab is poisonous, allowing her near you is perhaps the greatest wrong your mother has done."

"Well, Merlin, entertaining as it is to hear you berate my mother on her wrongs – you should have heard what she would say about you – I can assure you there is no need to trouble yourself on that question any longer. My mother is beyond earthly concerns now." Merlin blinked.

"Morgan is dead?"

"Mmm, indeed." Mordred shrugged this information off as though it meant nothing to him. "It's just me and Auntie now." His eyes lit up at the end of that sentence.

Merlin sighed, "If you had any sense, you would get away from her."

"If you had any sense," Mordred snapped, "You would appreciate all that she has done for you. She made you, gave you power, would have given you more. But you were too weak to take it. Well... that doesn't matter now. Now, she has me – and I assure you that I am not too weak."

"You are dancing to Mab's tune," Merlin replied angrily, "If you see anything other than unquestioning obedience as weakness, then I pity you."

"I don't want your pity," snarled Mordred, slamming his fists against the table. Merlin heard the sounds of wood splintering. Mordred sat back, rubbing his hand thoughtfully, pulling his expression back under control, "And there is a great deal that I question. For example: after all you've done, why doesn't Auntie Mab want you dead? You are nothing but a nuisance to her plans. She has me now. So I came to see for myself – what is it about you that makes her want to keep you alive?"

Merlin almost choked on his own surprise. For the first time all evening, it felt as though Mordred was actually being genuine. He didn't want to know more about his father, or punish Merlin for keeping him away from Camelot. This wasn't about Arthur at all.

"That's what all this is about? Jealousy? Over Mab?" Merlin didn't know whether to laugh or cry – laugh because it seemed ludicrous and cry because if nothing else, this proved that Mordred was completely Mab's creature.

Mordred shrugged, "I can't say that this visit has been terribly enlightening. If there's a use to keeping you alive, I certainly don't see it. Auntie's not given to sentimentality. But apparently, for you she's willing to make an exception." His fingers were digging into the table, leaving crescent shaped marks, "You're her precious pet wizard, you were her first hope. You were hers, I'm just Arthur's."

"Well if it makes you feel any better, and keeps me from losing my table, then let me assure you: She's all yours," Merlin replied drily, "For all the good it will do you. Mab brings harm to all that she touches, Mordred, and for the life of me I cannot tell whether it is always on purpose or not."

Mordred took his hands away from the table, carefully, "You speak as though I need your permission, cousin. As though this is something for you to give, not something for me to take."

"I thought you said you weren't going to kill me, Mordred." Merlin spoke evenly. He still pitied the boy, but that did not mean he wouldn't defend himself if the need arose. And from the burning dislike in Mordred's eyes, he was beginning to suspect that it would.

"I said that I didn't come here to kill you. And that Auntie Mab didn't want you dead. That's not quite the same thing. Oh, but don't worry cousin. You're safe for now." Mordred began to rise, "I'm nothing if not thorough. First, you'll see your precious Arthur die. Then his loyal knights go up in flames." He brushed some splinters of wood off his fine clothes, "And then," he glanced back at Merlin, his Mab-smile back in place, "Then it's time to wipe the Christians off the shores of Britain. Perhaps I'll start with Avalon. Perhaps I'll start with... what was her name? Oh, that's right. Nimue. By the sounds of it, she should be quite easy to find. Or perhaps I'll just feed them all to dragons, and save myself the trouble." Merlin stood to face Mordred, his own eyes flaming now, hands twitching as though with the urge to strangle Mordred where he stood.

"And when I've done all of this, when I've proven myself as her champion, do you really think that Auntie Mab won't grant me anything I wish? And that's when I'll kill you."

"And what if she doesn't," Merlin challenged, "What if she never quite comes around to the idea? What if you always stay second best?" It was spiteful, perhaps, but Mordred's threat to his own loved ones had given him the urge to hurt back.

Mordred shrugged, "Well, then I suppose I'll be king," He bent swiftly and scooped his dagger up from the floor where Merlin had flung it earlier, twirling it around in his fingers, "And she'll need me even if I do kill you." He tucked the knife into his belt, and made his way out of the hut, waving carelessly at Merlin as he did so, "It's been a pleasure catching up, cousin. I'll be seeing you again soon."

Merlin watched him go, hands shaking, and not sure for a moment whether it was Mordred or Mab that he pitied more.