"Gaius told you."

It's not a question. Not really.

Merlin knows. Even if Gaius hasn't told him. Even if Gaius hasn't said a word. Merlin knows. Merlin always just sort of knows, and Arthur knows Merlin knows, he can read it in Merlin's face, see it in his eyes, and it's—God, it's horrible to think like this, and Arthur knows that, he knows, but it's a bit of a relief—no, it is a relief, it is, not a bit, not sort of, it is a relief, and that's the bare and ugly truth of it.

It's a relief. In a hundred thousand ways, it's a relief, to know Merlin knows, to know he doesn't have to say it, not yet, not here, he doesn't have to talk about it, he doesn't have to push the awful words out past the tight knot at the back of his throat, he doesn't to have to hear the words again, and from his own mouth this time—Guinevere can't—or maybe I can't—I don't know, and Gaius can't say, but Guinevere can't, or I can't—I'm not—or Guinevere's not—we're not—we can't—

No, Arthur doesn't have to say it.

Arthur doesn't have to say it at all.

Because Merlin knows, just like he always, always knows.

"I am so sorry," Merlin says, and any moment now, all that pity in his eyes will brim up, spill over, and run down his cheeks like tears. "I-I am—I am so sorry."

"I just—I thought—" Arthur bites down, hard, on his bottom lip to stop himself there, right in the middle, before he can go on, before he can say I just thought we weren't trying hard enough, I just thought maybe we could make it happen if we only wanted it more, and I did, God, Merlin, I did, I wanted it so much, I wanted it more than I have ever wanted anything in the whole world, and I can't, or Guinevere can't, not ever, and it doesn't matter how much I want it, how much I wish—

"—I thought," he says, softly, "I just thought we still had a chance."

I thought I had a chance, he thinks, but he doesn't say, to hold my own child one day. I thought Guinevere and I had a chance, I really thought we had a chance, but we don't, and I see now we never did—

"I'm sorry," Merlin says, again, and his words hardly over a whisper this time, "I wish—I-I really wish there was something I could do—"

Arthur shakes his head and don't be an idiot, he wants to say, except that knot is back in his throat, and he can't talk around it, he can barely breathe around it, but don't be an idiot, Merlin, don't try and fix this, you can't, you know you can't, you can't fix this, even with all your magic, even with all the magic in the world, you can't, you couldn't—

—but—but wait, that's not—

That's not true.

That's not true at all, is it, because Merlin could fix this, no, Merlin can fix this, and maybe—

—maybe—

"Merlin," Arthur says, and his mouth is dry, and his stomach twists and turns, over and over and over again, because he knows this path is dark, bad, wrong, and maybe it will destroy him like it did to his father, maybe it will turn him into his father, all over again, but damn it all, he has to try, "would you—would you give me an heir?" He never looks away from Merlin, he never lets himself look away from Merlin, because if he does that, he knows he'll break off, he'll stop, he'll lose his nerve. "If I asked?"

Merlin stares at Arthur for a very long time—in the silence, Arthur can hear the distant bustle of servants on the other side of the door, the clank of the knights' armor, the swish of long cloaks and skirts, the talk and the laughter, but he won't say anything, not until Merlin does, and it looks, right now, like Merlin isn't ever going to say anything at all, ever again, but—

"I would do anything for you, Sire. You know that."

Arthur's stomach lurches—the fear of it jolts all the way through him like a strike of lightning, like a crash of thunder, and for all of a moment, he thinks, this is it, I'm going to do it, I'm going to ask him, right here, right now, he's said I'll do it, if I ask, he's said he'll do it, all I have to do now is ask, but he—

—he can't.

He wants it—God, he wants it, so much, and he knows it would be so easy, he wouldn't need to say a word, he wouldn't need to say anything, because Merlin knows, Merlin always just knows, but—

This is the way my father lost my mother, and what if it's the same, what if it all works out the same, even if I lay down my own life for this, what if that's not enough, what if this is the way I lose Guinevere?

Arthur swallows.

"No," he says, finally, and God, it's the hardest thing he has ever said in his entire life, but it's the right thing to say, it's the right thing to do, and he knows that, he knows it, so he only lets his heart ache, one last time, for the little one he will never have.

"No, Merlin," he says, "don't."

Notes: don't come at me with Gwen was secretly pregnant with Arthur's child and just didn't know until after the battle at Camlann, and the writers didn't mention it because it wasn't relevant to Arthur's journey :) because Uther and Ygraine couldn't have an heir, and Uther decided to go ahead and have an heir anyway in the dumbest and most dangerous way possible, and Arthur and Guinevere also can't have an heir, but Arthur finds a rogue brain cell, unlike Uther, and that's the whole reason i wrote this pile of garbage in the first place.