Disclaimer: Once Upon A Time belongs to ABC.
So it's clear that Snow finds out that Charming isn't James sometime before the events of Lady of the Lake. But we haven't been shown how or when she finds out. So I wrote this.
"Get down!" Snow hissed, and without further ado she grabbed Charming by the arm and hauled him unceremoniously to the forest floor beside her. He ended up on his back in the dirt, Snow crouching next to him in a hollow behind a fallen tree. She knew this forest better than anyone, so he didn't have to ask her why she had decided to throw him to the ground. He just stayed perfectly still and silent, watching her peer over the top of the rotten tree trunk that was their hiding place.
Moments later, she ducked her head and locked eyes with him. She drew a finger to her lips, to which Charming just gave a small nod. Sure enough, the sound of horses and marching feet soon reached his ears. Snow huddled a little closer to him and closed her eyes.
Charming could tell by the clinking of mail that these were King George's men, not Regina's. But they both wanted them dead, so that distinction didn't really make much of a difference. He found himself holding his breath as the noise grew nearer. By the sound of it, there were a lot of soldiers approaching. Two, maybe three on horseback, the rest on foot. Charming glanced at Snow, but her eyes were still shut. It sounded like they were marching right past their hollow, and Charming was sure any moment someone would spot them.
But the marching faded off in a direction perpendicular to the path Snow and Charming had been following. Gradually, peace settled back over the forest. Charming allowed himself to breathe again, and Snow only opened her eyes when she heard the birds resume their singing. She sighed in relief and sat back against the tree trunk. Charming sat up and scooted beside her.
The two of them were headed to a rendezvous point deep in the woods where Red and the dwarves were gathering their forces. Charming had awoken Snow and asked her to marry him barely two days ago, and so far they had spent all of their time as an engaged couple running from his father and her step-mother.
His father… Charming frowned at the thought. He knew Snow suspected something, but she still believed him to be James. Probably not the best way to start a life together.
Charming glanced over at his betrothed. She was breathing normally, but she wouldn't meet his eyes, and that was a sure sign that she was rattled. He took her hand in his without preamble, unconsciously rubbing his thumb over her ring, and she finally looked over at him.
She smiled at him, her eyes warm despite her obvious weariness. They leaned in simultaneously and their lips met in a kiss, brief but urgent, and when they broke apart Charming squeezed her hand.
"I have to tell you something," he whispered.
"Can it wait?" Snow replied distractedly as she leaned up a bit and glanced over the tree trunk.
"No," he said seriously, and that was all it took. She turned her full attention to him, concern wrinkling her forehead, and nodded.
"Okay," she said simply. "What is it?"
Charming took a deep breath. It took all of his resolve to maintain eye contact with her.
"I… I'm…" he stammered, and she just waited patiently with a ghost of a smile on her lips. He sighed again, frustrated. "I'm not Prince James."
Snow's lips parted a bit and her eyebrows shot up. She just stared at him like that for a moment, and he was relieved to see that she didn't appear frightened or betrayed. No, she just looked confused.
"My name is David," Charming began quietly. Snow's eyes softened a bit, but the confusion didn't leave them, so he squeezed her hand and continued. "Prince James was my twin brother."
Charming paused, giving her a moment to let that sink in. Her eyes narrowed a bit as she scrutinized him, and it made him somewhat nervous, but then a faint smile appeared on her lips and she nodded for him to go on.
"James and I were both born on a farm," he continued. "King George and his wife were unable to have a child, so they made a deal with the Dark One. He came to my parents who were very poor, and they gave up James in exchange for the farm."
He stopped again, finally glancing away from Snow. He was still getting used to the fact that this was his story.
"Until a few months ago, I was just a shepherd," he continued thoughtfully.
"Now I have to tell you something," Snow said suddenly, and he looked at her in surprise. She was smiling at him fondly, and he just nodded for her to go on. "I knew you weren't Prince James the moment you first told me your name."
He stared at her, his mouth hanging open. "How… how did you…" he stammered, but she just laughed lightly and shook her head.
"I met James when I was a little girl," Snow said, and Charming's mouth fell open again. She laughed again. "You're surprised? Royalty loves to visit other royalty. You know, show off how well their kingdom is doing, marry off their children, things like that."
This time, it was Snow giving Charming a moment to process. He attempted to speak, but found he had nothing to say, prompting Snow to laugh again.
"I was eight years old when King George arrived for a meeting with my father, and he brought his son, Prince James," Snow continued, looking down at their intertwined hands as she remembered. "He was a spoiled, rotten little boy. He pulled my hair when nobody was looking, so naturally I shoved him and he happened to stumble and fall on his little royal butt." Snow shook her head slowly, a grin on her face. "I was in so much trouble. But it was worth it to take that brat down a peg."
Charming burst out laughing, and Snow soon joined him. They tried not to make too much noise, but of course that just made them laugh harder.
"And then you came along," Snow said when their giggles finally quieted. She met his eyes, and they just smiled at each other for a moment. There was something between them that she was just getting used to, something silent and profound, and she didn't need to say a word to know what he was feeling. "And you were kind, and humble, and you saved my life a few times," she continued, her voice softening as she spoke. "And on the Troll Bridge, you told me your name was James. But I knew it wasn't."
"How could you be sure?" Charming asked quietly. "You hadn't seen James in years. How did you know he hadn't just… changed?"
"Your eyes," she said simply. He cocked his head in confusion, and she just shrugged. "You hate being dishonest. I could see it. You told me your name was James… but you didn't want to. You wanted to tell me the truth." She smirked. "Because you'd gone and fallen in love with me."
Charming rolled his eyes. Snow laughed in response, and he let go of her hand to loop an arm around her waist. She leaned into him comfortably, closing her eyes for a moment of peace.
"So what did happen to James?" she asked curiously after a few moments. She didn't open her eyes, just settled into him a bit further. So Charming grinned and told her the story as he knew it. James' death, George's deal with Midas, and his escape with the help of Abigail. This bit surprised Snow, especially the part involving the Siren, but Charming convinced her that Abigail was more than just a nag with a bad attitude and that they had parted friends.
"Did Abigail know who you really are?" Snow asked, glancing up at him.
Charming shook his head. "The only people who know are Rumplestiltskin, King George, and my mother," he listed slowly.
Snow gripped his arm suddenly. "Your mother," she said, alarmed. "She could be in danger. King George is after us, and he knows where she is. We have to-"
"I've already sent her a message," Charming cut her off calmly. "She's gone into hiding. I told her I would come for her when our forces are strong enough to keep her safe with us." Snow let out a breath and sat back in relief. It took her a moment to notice Charming was beaming at her.
"What?" she asked.
He laughed lightly. "You're so concerned for her even though you've never met," he pointed out.
Snow shrugged self-consciously. "I just… I don't want you to lose your mother," she murmured. Then she smiled softly and glanced at him. "Besides, she'll be my mother-in-law soon, right?"
Charming just stared at her for a moment before he grabbed her by the arms and kissed her fiercely. She laughed against his lips and draped her arms around his neck, running a hand up into his hair. He pulled his mouth from hers just as abruptly as he had started, and her eyes fluttered open to meet his in a questioning gaze. He smiled.
"I love you so much, Snow," he whispered.
She smiled shyly, a blush coloring her cheeks. For some reason, she was only ever shy when he told her he loved her. It was as if she wasn't used to being loved and she didn't know how to handle it. He intended to change that.
"I love you too…" she trailed off, looking at him thoughtfully. She tilted her head to the side and gave him an appraising look. He quirked an eyebrow in question and she broke into a smile. "David."
The sound of his name, his real name, sent a jolt through him. She let out a quiet laugh and pulled away from him. She got to her feet and stretched her arms over her head. Charming stood up beside her and they both looked at the tracks left by the soldiers. They had passed so close, it was a miracle they hadn't been seen.
The two of them shared a long look. Then Snow smiled slyly and held out her hand.
"Nice to meet you, David," she said airily.
He laughed and drew her hand to his lips.
"Please, call me Charming."