Summary; Though they were bros in all sense of the word, there were some things that Chrom would never let even Robin have

Pairings; Male!Robin x Lissa

Info: Based on Chrom and Maribelle's B Support. Because I think even Chrom has that brotherly overprotectiveness deep within him

Disclaimer; I own nothing

Sister Complex

(Male!Robin Edition)

The first thing that Robin heard was a loud slam. He halted before the doorway, blinked, and ultimately sighed, debating whether he should order a new table now or later. Their leader was always prone to breaking things regardless of how hard he tried not to. And all that trying led to Robin ordering about five different tables.

'He honestly needs to learn how to control his strength...'

After maneuvering around the door to safely navigate passed a bucket - he could not be fooled that easily, he thought with a smirk - he observed the Ylissean royal's slumped posture, his head banging absently against the table. Robin felt a sigh of relief at the realization of no evident damages and proceeded to walk towards him.

"Are you trying to test how hard your head is? If you really want to break this table, I think you have to hit it a little harder," he teased.

Chrom did not offer any reply, continued to knock his head repeatedly against the table. Robin just stared, torn between laughing and rolling his eyes. He settled for a quick breath of amusement and a shake of his head.

"Alright, before you really do break something, mind telling me what's up? It's rare for me to see you so distressed."

Finally Chrom stopped. "It's Lissa," he groaned out, his voice muffled against the tabletop.

"Lissa?" The tactician caught himself and paused, looking quickly down at the chair and swiping away a whoopie cushion. "Why? What's the matter with her?"

"Everything!" Robin felt his eye roll. "You don't think that Lissa is... seeing anyone. Do you?"

He blinked at such a frank statement. Once. Twice. Chrom raised his head to stare at him with an all too serious face, proving this was a legitimately serious question. Robin cleared his throat, trying his hardest to conceal his laughter.

By Chrom's furrowed brows, he doubted he was successful. "Come on. Please don't laugh!"

"But you can't blame me! I never realized you had a siscon streak." Chrom frowned, but Robin remained smiling. "If it makes you feel better I have been supporting her for the past few battles and talked with her upon numerous occasions. I don't think Lissa mentioned being interested in anyone. Why do you think so?"

The prince dropped his gaze to the table. "I was just talking to Maribelle, and she said some things got me concerned over her..."

"Maribelle is just overprotective. I should know. She scolds me all the time."

And all those times were about Lissa. He flinched, recalling when Maribelle glared at him, reprimanding him endlessly about the importance of Lissa's safety, threatening that if he ever hurt her, Maribelle would have his head...

'Like I'd harm Lissa. If anyone should be worried it would be her behavior towards me.'

He tensed and quickly turned the flower on the table to the side, watching in triumph as it sprayed water out into space.

'Ha, Lissa can't fool me that easily.'

He felt his smile vanish when he looked back at Chrom, his brows furrowed, gaze focused on a spot on the table.

"It's not like I don't trust Lissa. I do let her have her freedom and her space. It's just I never realized just how quickly she grew up. I wouldn't be surprised if she did have her eye on someone. She is at that age after all..." Chrom frowned at the thought and dropped his head back onto the table with a resounding plunk.

Robin felt a gasp rush through his lips. He kicked away a box of frogs from that sat underneath them and leaned forward, first studying the table - still unscathed, thank gods - then the Ylissean royal.

"Well there isn't anyone stupid enough to mess with Chrom's little sister. Besides, Lissa is a smart girl. She can hold her own."

Still Chrom responded nothing more than a heartfelt sigh, resuming banging his head against the tabletop.

"Hey, why not just go to her and seeing what wrong? That should help ease your mind," he offered, hoping that would lift Chrom from his slump.

Instead, his words seemed to do more than that. Chrom's eyes widened as an idea flashed into his mind.

"Yes, of course! That's brilliant, Robin!" The tactician blinked, failing to comprehend. He flinched when Chrom slammed his hand against the tabletop, his gaze flickering down momentarily to see if there was a scratch. "I will investigate and see if Lissa has an interest with anyone in our army! It's a perfect plan!"

Despite his enthusiasm, Robin only looked at him with a questionable stare. "So... you plan on stalking her?"

"No, it's not stalking. It's an investigation."

"But wouldn't it be easier to just ask her?"

"No, Lissa may get the wrong idea and think I don't trust her. Or think I'm too overbearing of her. Or–"

"Or think you're being a total overprotective siscon?"

"I prefer to think myself as moderately protective, thank you."

He rolled his eyes, but Chrom remained unfazed, beaming at the sheer brilliance of the idea. Robin grabbed a book from the side and slid it in front of him. "Now I think we should focus. We do have a battle coming up after all, and–"

Robin's words were clipped from his tongue when a puff of smoke erupted from the book. Chrom jumped out of his seat while Robin sat completely still, coughing.

"What in the name of Naga was that?" Chrom asked, placing a hand instinctively on his blade.

"Oh, I think I know what it was." He wiped some dust off his face, and his eyes narrowed. "And, I know exactly who did it..."

"Haha! Gotcha!"

At the sound of the voice, they both spun around to see Lissa peeking out from the doorway, her smile bright and triumphant.

Robin appeared less than amused. "Lissa! What did you do with my book?!"

"I don't know... but if you want to find out, you have to catch me!"

And in a blink of an eye, Lissa raced out into the hall with a certain tactician tailing furiously behind her.

"Great thinking, Robin! You go keep her distracted while I investigate!" He smiled cheerfully to himself and at his plan. "Now where do I start..."

It would be hard to do it by himself though. Robin was busy with distracting his sister, leaving him indisposed. He needed help, but it had to be someone he could trust, someone who cared about Lissa as much as he did, who could be extremely thorough to the extent that could be construed as overbearing...

An idea struck him once more. He slammed his hand onto the table, earning a flinch from the distance. He knew exactly who to ask.

"Milord, I finished my end of the investigation as you asked me."

"That's great-" Chrom jumped when Fredrick dropped a pile of paperwork on the table. He blinked, stared, and finally asked, "Why is there so much paperwork?"

"I was just being detailed. I noted all her activities in clear chronological order like you requested me too," he answered, his chest puffed out, and smile bright on his lips.

"Well perhaps you took me too literally." He sighed and shook his head. "Could you summarize your report and note anything unusual?"

Fredrick blinked and looked down at his stack, quickly paging through it. "Well more or less her activities have been normal... Though one time she asked Gaius's assistance to help her bake something."

Chrom nodded his head in consideration. Gaius was already engaged with Cordelia so there was little chance he could be the culprit. Maybe she wanted to actually improve her cooking abilities and produce something that was well... edible.

"Hey guys!" Robin trotted inside and held out a platter. "I got some leftover lemon tarts! Do you want some?"

Chrom smiled and happily took on, nodding his head in thanks. Fredrick only stared, watching as Robin trotted off with the baked goods in his hands. A thought popped into his mind, but he immediately dismissed it, paging through the stack of papers.

"And there was also a moment when she was in the armory with Vaike."

Chrom swallowed the rest of the tart and considered it for a moment. Though it was unusual for Lissa to be in the armory, Vaike could not be the one Lissa was interested in. After all Lissa viewed him like an older brother while Vaike seemed far too interested in Panne.

"Hey, guys, I'm off to practice." They turned to see Robin walked passed the doorway, sporting a sparkling Levin sword in his hands.

"Taking great care of your equipment I see. Looks brand new!" Chrom interjected.

"Nah, you should thank someone else for polishing my blade!" He smiled and waved, heading off into the practice room.

"That's nice to hear our fellow Shepherds helping one another," the prince noted. "Weapon maintenance is important after all."

Fredrick seemed unable to hear him, his thoughts focused on the shining blade. He dropped his gaze back to the paperwork, considering something. No, it couldn't be...

"And finally. The other day I noticed her coming back form town with Virion after purchasing something, though I have little idea what the contents were."

The prince nodded his head, but he quickly dismissed Virion. Despite his philandering ways, he was a close and trusted comrade that always held Lissa with respect. Besides, he doubted he would get very far with Cherche's and Minerva monitoring him.

"Oh, I forgot I need to put this back too."

The prince and the knight turned and watched Robin shuffle passed the doorway again, book tucked underneath his arm.

"Oh, I haven't seen that one before. Is that a new strategy book?" Chrom asked.

"Yeah, it's a very rare copy! I got it as a gift!" He replied cheerfully, looking at the book with reverence. "Well I need to put this back in a safe place before I train. See you later!"

Chrom waved goodbye, a pleased smile on his face. "Wow. It's heartwarming to see Robin getting such nice treatment lately. He definitely deserves it considering how hard he works, don't you think so, Fred...?"

His smile vanished when he looked back at Fredrick, whose lips were tight, and brows knitted in deep concentration, his gaze burning out into the distance.

"Is everything okay?"

"I'm just... thinking." Fredrick glanced back down at his paperwork, processing something. Soon a certain light flashed in his eyes. He gripped the paperwork tightly, his armor rattling slightly as his arm shook. "Pardon me, milord, but I believe I still have one more source to explore in order to get to the bottom of this matter."

Before Chrom could question him further, Fredrick strode off.

"Huh. I wonder what's that all about." Perhaps he'll never know. Chrom just sighed and shrugged his shoulders.

Robin instinctively paused when he heard the sounds of light banging. His lids slid over his eyes as a sigh rushed through his lips, running his fingers through his hair. Even though he definitely was not surprised by the sound, he still couldn't shake his concern. The poor thing managed to survive their leader's onslaught for awhile now. He just wanted the streak to last a little longer.

Steeling himself and praying to Naga to ensure the table's safety, he entered the room. "So how's the investigation going, Chrom?"

"Fruitless thus far..." Chrom released a heavy sigh and ceased hitting his head against the tabletop, laying his head desolately against it. "Even with Fredrick's help, we haven't gotten any closer to figuring out if Lissa has a crush or not."

"Really? Even with Fredrick's help? That's hard to believe." Robin took his seat, placing his strategy book and a plate of pastries on the table. "Here, have one of these lemon tarts. They'll help you feel better. They're really good."

Chrom accepted one passively and took a large bite. "And it's not to say that he wasn't thorough. He reported some things he thought were unusual, but seemed fairly normal to me..."

"Well what did he say?" The tactician asked and took a bite of the tart, releasing a sigh of contentment. Damn, they were good.

"Well he told me he saw Lissa working with Gaius to bake something... You know how my little sister bakes. It's always a disaster whenever she tries."

"That... is true."

Robin paused a moment and looked down at the tart before quickly dropping it back onto the plate. No, it was too improbable. Purely coincidence. He shook his head and pushed the plate aside, hoping to banish his suspicions from his mind.

Chrom didn't seem to notice and continued on with his laments. "Then he saw her with Vaike hanging around the armory... She never liked handling heavier equipment. Maybe she was helping with maintenance?"

"M... maybe." Robin could not help, but think about his Levin sword, the polished steel feeling like hot iron against his waist. Still he refused to believe it, holding fiercely to his denial. It truly was impossible. She was a princess after all. There was no chance that she could possibly...

"And I suppose this is a little strange, but Fredrick saw her going out into town with Virion. She was just probably buying supplies though. I don't know why else she would go."

Robin was unable to utter a word. All he could do was stare at his new strategy book, feeling his face grow hot, his heart hammer against his chest.

Chrom reached over to eat another lemon tart when he noticed Robin's disposition. "Hey, are you alright? Your face seems a little..."

"I'm fine!" The Ylissean royal only stared. The tactician cursed under his breath and took a deep breath, fighting to banish the heat from his face. "Just so you know, Chrom, you are my best friend and comrade."

"Yes..." He only blinked.

Robin slid his seat away from the table and focused his attention on the fabric of his sleeves. "And I would never do anything to hurt you or Lissa. I care about you both a lot."

"Of course, Robin. I trust you with my very life." Though he did not understand why he would bring up something like that now of all times.

He felt his brows furrow as he watched the tactician squirm anxiously in his seat, eyes flickering over to him then down to the table. Chrom didn't get why he was acting so strangely. Was there something Robin knew that he didn't?

Before Chrom could question him about it, they were interrupted by a loud rap on the door.

"Robin, I got some new sweets, and I was hoping you wanted to sit with me to try-" Lissa's words fell from her tongue when she noticed her brother in the room. She smiled. "Oh, hey there, big brother! I didn't know you were still having your meeting with Robin! I thought you guys would be done by now."

Robin could not find the voice to speak. All he could do was watch as Chrom stared blankly at his sister, processing something in his mind. He tensed when Chrom turned to look a him, eyes wide, studying, thinking.

He looked back towards Lissa. Then turned towards Robin.

Lissa. Robin. Lissa. Robin.

And all too suddenly, the realization seemed to struck Chrom harder than he expected.

"By the gods. Why did I never think of this before." He slammed his hand roughly onto the table, causing Robin to jump out of his seat. "You! You are the foul heathen that threatens my sister's purity!"

"W...what?! N...no! No, Chrom it isn't like that!" Robin swallowed, watching Chrom's hands press harder into the table, leading to form a small crack.

'No, not that.'

"Oh yeah?!" Robin flinched, watching as the crack grew a fraction of an inch. "Then tell me now that you have no interests in my sister romantically. Then maybe I will believe you!"

He slammed his other hand onto the table, making the crack more pronounced. Robin felt something inside him also break, reducing him to a stammering mess.

"Um, um..." He felt his eyes flit over to Lissa, her blue eyes wide, expectant, hopeful...

He felt himself flush for considering the last thought and dropped his gaze to the cracking table.

He was saved from answering when Fredrick burst into the room.

"My lady, I apologize, but I cannot keep quiet any longer." He marched forward and slammed his lance against the tabletop, causing the table to bend and shudder against its weight. "I shan't allow Robin to soil Lady Lissa with his impure intentions any longer!"

"But I never had those kinds of intentions! I never did any of those things!"

"But do you think I'd even let you have Lissa so easily?" Robin promptly shut his mouth, watching as Chrom unsheathed Falchion

He froze when the prince pointed his blade to him. "If you desire Lissa's hand, you need to prove yourself to me through a match!"

"Her hand? O...oh wait. That's going a bit far don't you–"

"And to me." He jumped back when Fredrick also raised his lance up to him, his eyes deadly serious. "Ready yourself, Robin."

"Come on, guys. You're being a bit overprotective and dramatic. Can't we just talk about things?"

He was answered by a loud grunt, watching as Chrom raise Falchion and slash it down onto the table, splitting it cleanly in half.

"I guess not." A little part of the tactician died. "Really, Chrom, that was mahogany..."

"That is enough talk. Pick a god and pray!"

"Your end has come!"

Robin had no time to mourn the table's loss. In a speed that he didn't know he had, he rushed passed Lissa and out the door, pursued by the blue royal and his knight.

"Chrom, Fredrick! Please don't hurt him!" Lissa pouted and crossed her arms over her chest. "I knew I shouldn't have told Fredrick when he asked... Those two can be so overprotective sometimes."

With a brother and knight like that, she may grow to be a lonely old maid. She sighed at the thought. Who knew getting a boyfriend was so hard?

A/N: I was daydreaming about what a Male!MU version of "Sister Complex" would be like so I decided to write another oneshot and see

Thanks for reading~