Notes: So, as anyone who has checked my profile lately knows, I entered the Merlin reversebigbang this year. It was equal parts fun and stress-causing, but I got my fic completed and posted on time. Anyone who wants to read the full thing now (post-beta but pre-edits-now-that-I-have-time-to-edit), head on over to ao3 (archiveofourown works/1424167), or I will be posting it probably a chapter a week (fifteen total) over here.
This is based on fantastic art by bloodsongs, which can also be found on ao3 (archiveofourown works/1422589), which I seriously recommend you check out. In addition to the gorgeous image of the wedding that was her first entry, she was also willing to draw an amazing second piece at my request, of Arthur angsting (who doesn't like that?) over his speech. Again, I recommend you head over there.
And, because I cannot say it enough, this fic would never have been finished (or, for that matter, started) without my incredible beta and bud, Daroh. You make my life and this fic so much better. (Also, any scenes that merit this an M-rating are entirely down to her and Detochkina, and you have no idea how much angst the pair of them caused me with their determination that I be specific)

Warnings: Language, sex, violence to computers, and a fuckton of angst (imperial, obviously). I hope you enjoy :)

Something old,
Something new,
Something borrowed,
Something blue.

X 1 X

"Arthur," Morgana calls, walking into his house without so much as a courtesy knock. Yes, Arthur has given her a key, and yes, they shared a womb for nine months and baths for several years after that, but the key is supposed to be for emergencies only, and the years in which Arthur shared everything with his sister are long gone. "You home, little brother?"

Arthur looks up from his place on the sofa to the door Morgana is closing behind her, resisting the urge to point out that fifteen minutes hardly counts, mostly because she laughed him out of making that argument at least a decade ago. "Do come in, Morgana. It's lovely to see you. Can I offer you a drink?"

"No," Morgana says, ignoring his sarcasm as she ignores everything else that doesn't suit her purpose. "Although you might want one. This isn't a social call, Arthur."

"Funnily enough, I hadn't thought it was. You've never visited anyone without at least two ulterior motives in your life."

Morgana smiles without humour, but then Arthur's jokes have never amused her all that much. She slips out of her coat and hangs it on one of the hooks by the door, then crosses the room without taking her shoes off, her heels leaving little indentations in the carpet that slowly fade like footprints in the sand. The sofa hardly shifts at all as she sits beside him, curling her feet up underneath her and never mind the leather.

"Arthur," she says again, so quiet he has to lean in to hear her. "Merlin is going to ask me to marry him."

Heart sinking through his stomach, Arthur forces a smile onto his face; Morgana may know him well enough to know that it's not real, but that doesn't mean he can't try for her. His sister. His best friend. He's happy for them. "Congratulations! I'm so happy for you."

Morgana's eyes narrow, and Arthur knows she knows his cheer is faker than Katie Price's tits. "Save it until he gives me the ring, brother," she says, drier than the Sahara, before turning on him with a disturbing intensity.

"Tell me not to," she says, wrapping her hand around his, talons shielded enough that she's not quite drawing blood. "Tell me to say no and I will, Arthur. Tell me to leave him and it's over."

For once, Arthur doesn't pretend not to know what she's talking about. It's far from the first time Morgana has made hints about his feelings for Merlin; she told him the same thing years ago, the first time Arthur walked into a room to find the pair of them kissing and refused to speak to either of them for a week without even realising why he was so angry. Tell me not to, she said. Tell me to stay away from him and it'll never happen again.

He'd laughed, then, mystified and lost, because Merlin was his best friend and Morgana was his sister and there was no reason for him to hate the idea of them together. No reason, he told himself, and continued telling himself right until he realised there actually was.

Today, he isn't laughing; he might still be lying to the rest of the world, might successfully have kept all the truths he cannot say from everyone but his sister, but Arthur has stopped lying to himself.

In the darker part of himself, the part he hates most of all, he thinks about doing it. Morgana wouldn't make him give a reason, not when she already knows it. She would just nod, smile like she's proud of him, and go home to Merlin one last time before packing up and moving out.

All Arthur has to do to stop them marrying is admit he wants to. Three words, don't marry him, and he will never have to watch the man he loves swear to love only his sister until he dies.

Three words, don't marry him, and Arthur will break two hearts, with nothing at all to show for it. Merlin loves his sister, will still love her even if the two of them break up. Arthur will never have him.

"I'm happy for you, 'Gana," he says again, because whatever choice he makes, he loses, and at least this way the two people who matter the most to him are whole and happy.

Morgana smiles at him, her expression equal parts joy and sorrow, so clearly relieved she doesn't have to keep her promise, so clearly sad that, even now, he just isn't as brave as she wants him to be.

She doesn't speak, though, merely sweeps to her feet and stalks out, disappearing with as little warning and as much drama as she arrived.