A/N: So this is an AU story, where Ygraine never died giving birth to Arthur. She had a baby girl called Ariana, but was shortly captured and killed by sorcerers, so Uther still hates magic.
First attempt at an OC so please R&R and tell me what you think.

Arthur/Gwen and Merlin/OC fluffiness.
Ever so slight spoilers for 3.06 but nothing too major.

Enjoy!

"Don't."

"I wasn't doing anything."

"Well, in case you do..." Arthur raised his eyes at his younger sister, then smiled to show he was joking.

Ariana laid her head in her hand and sighed loudly, slumping forward in Arthur's chair.

"Don't slouch," Arthur told her absent-mindedly as he sharpened his sword. She adjusted her position with an accompanying sigh. "And stop sighing." She made a face. "Act like the Princess that you are."

"Arthur!" She moaned. "Will you stop behaving like Father for just one minute?" She sighed again, leaning back in the chair in a very undignified way. She was glad he chose not to comment.

He smiled. "I know you're frustrated."

"Really?" She asked, words drenched in sarcasm.

"And I know what's causing it,"

She turned to face him. "So do I... I'm looking at him!"

"It isn't me you're frustrated with little sister," Arthur said softly.

"You're right," she muttered. "It's this voice that's constantly talking, right in my ear... Oh wait, it is you!"

Arthur chuckled lightly. He put down his sword and sat on the table, facing his younger sister. "I see the way you look at him."

Ariana suddenly looked uncomfortable, almost guilty. "I don't know what you're talking about," she mumbled.

"Don't play dumb with me Ariana," Arthur said. "I've known you your whole life."

"And?"

"I know when you're lying." He looked at the expression on her face and sighed. "I can see it in your eyes."

"You don't know what you're talking about," she said. She lowered her gaze and stared at the floor.

"Your heart seems to melt when he looks at you." She looked up. "When his hand brushes against yours, you feel your heart stop." She held her breath, waiting for his next words. "Yet every time he looks at you, all you feel is pain." Her eyes began to fill. She blinked and looked away, but still listened. "... Because you know it can never be."

She fought the urge to cry, even though she desperately wanted to. Each word Arthur had spoken was the truth. How can I live, she thought, knowing we can't be together?

"I know," Arthur said, "because I feel the same way about Gwen."

Ariana managed a small smile. "I know."

"What?" Arthur was slightly alarmed. "When did you find out? Who told you?"

"I've known for some time my brother," she said. "And no-one told me. Anyone who spends two minutes with you both can tell how you feel."

Arthur smiled. "Ariana, what I'm saying, is that I know how you feel."

The smile faded from her lips and she stared at the floor once more. "It's not fair," she said, her voice cracking with emotion.

"I know."

She sniffed and looked up at Arthur. Her eyes were shinning, brimming with tears. "I don't care," her voice barely a whisper, "That he is just a servant. To me he is so much more."

Arthur stood up and walked to his sisters side, placing a comforting arm around her shoulders. She took his hand and gripped it tightly. "He is your light in the dark."

Ariana sniffed again. "He means everything to me."

"I know he feels the same way."

"How do you know?" She looked up at her older brother, a frown creasing her brow.

Arthur smiled at her and brushed a stray lock of blonde hair from her forehead. "Because he looks at you in the same way Gwen looks at me... He may be an incompetent, lazy, idiot of a servant-"

"Hey," she said warningly, but a smile found its way onto her lips; she knew he didn't mean it.

"But," Arthur said, emphasising the word, "he is a dear friend. His feelings for you burn as strong as the sun itself."

A tear rolled down her cheek and splashed onto her dress.

Merlin was right- Arthur could be a stuck-up arrogant prat sometimes... but he'd always been there for Ariana, offering a hand to hold, or words of comfort, when she needed it most.

"But," she said uncertainly, "what do I do now?" Ariana knew she would never be able to court a servant- her Father would never hear of such a thing.

"Tell him how you feel."

"What good will that do?" Her eyes began to fill once more. "How will knowing what we feel for each other, change centuries of laws and tradition?"

"Love is not governed by any laws, Ariana. Love has no rules; no regulations." Arthur sounded wiser than a man of his years, yet he made perfect sense. "You should not have to marry for the sole purpose of the Kingdoms prosperity... you should marry for love."

Ariana smiled. She knew he was talking about his recent state of affairs with Princess Elena, but the principal was still the same.

She stood up, hugged her brother and planted a small kiss on his cheek. "Thank you, Arthur."

He smiled as she left the room.

Merlin was finishing putting away books and potions for Gaius after running around for Arthur all day. But he felt a smile cross his lips whenever he thought of Ariana.

The young Princess was a true beauty, needing no make-up or fancy hairstyles. Her blue eyes were the colour of the deepest ocean and made Merlin's heart flutter in his chest, like the wings of a bird. Her hair was golden blonde, and cast the softest glow when hit by the rays of the sun. Her lips, full and soft, had Merlin wondering what they would feel like against his own on a regular basis. And when she smiled... his whole world seemed to stop.

Her beauty was not the only quality he admired. She was strong and courageous, like her brother, yet she was graceful and seemed so delicate. She had an air of superiority, yet she was humble in her approach to dealing with others... She was everything Merlin had ever wanted.

His smile faded and he sighed. The Princess would never look twice at me, he thought miserably. She is of royal blood... I'm just a simple peasant. What could I possibly hope to provide for her? She deserves nothing but the best.

He heard the door open. Thinking it was Gaius, he didn't bother looking round and continued to tidy.

"Merlin?"

He stopped dead, heart thudding loudly against his ribcage. He spun around a saw Princess Ariana standing in the doorway.

"My Lady," he said breathlessly, bowing to her.

She smiled and he felt his heart melt. "I... I came to tell you something," she said.

"Is anything the matter?" Merlin asked.

"No," she said, a little too quickly. She blushed and continued. "No, it's just... I came to tell you... I..." She seemed to be struggling to find the right words to say. "... I am in love."

"Oh." Merlin felt his heart grow heavy and sink to the pit of his stomach. He managed to force a smile. "I am happy for you." Good, he thought, although he felt his heart slowly breaking...She deserves someone who will make her happy...

She frowned slightly. "Don't you know who it is I love?"

"I wouldn't know my Lady," Merlin said politely.

"The man I love is... loyal and brave in the face of danger. He is kind and thoughtful, always putting the needs of others before his own. He follows orders, but challenges his superiors when the need arises." Merlin frowned slightly. "Merlin, the man I love is... is standing right in front of me."

Merlin's breath caught in his chest. His heart started to swell with joy; he feared his chest would not be able to contain it.

"You- you love me?" Merlin stammered.

Ariana nodded, her eyes brimming with tears. "I cannot deny my feeling any longer."

"But what about your father?"

"I don't care," Ariana said, "He is wrong. Titles mean nothing when you love someone."

"If he found out..." Merlin shook his head, unable to continue.

"He won't."

Ariana strode across the room, closing the small gap between them. She took his face in her hands and pressed her lips to his. Merlin was slightly taken aback, but quickly recovered and wrapped his arms around her waist. For a few moments they stood there, their lips moulded perfectly for each other.

Ariana broke away and looked into Merlins eyes. He saw that her own were brimming with tears, but there was a smile on her face. "I love you, Merlin."

He found himself ginning like an idiot. "I love you too, Ariana."

They stood and held each; for how long, Merlin didn't know. All he knew was that he had the woman he loved in his arms, and she loved him.

Outside the physician's chambers, Arthur and Gwen listened to the conversation that was going on the other side.

"We shouldn't be eavesdropping, Arthur," said Gwen, although she couldn't resist listening herself.

"I know, but I want to make sure he has nothing but the most honourable of intentions." He looked a Gwen with a serious look on his face, which broke into a grin when she raised her eyebrow at him.

"We both know that he does." She smiled. "When you are king," she placed a hand on his cheek, "you can change the law, so love cannot be restricted."

Arthur smiled and kissed her lightly on the lips. The broke apart abruptly when they heard someone coming. They gave each other's hand a squeeze and parted, going their separate ways.

For now.