John entered the flat and sighed when he saw the pieces of a suit and dressing gown strewn across the living room floor. He was getting sick of cleaning up after his flatmate, and had finally reached the end of his- rather impressively long- tether. Slamming the front door closed he stormed over to Sherlock's room and threw the door open with a bang.

"SHER-" John stopped short, staring open-mouthed as Sherlock and Mycroft sprang apart. Mycroft instantly pulled the covers up over his naked form, blushing furiously and staring ahead at John, yet not quite meeting his eye. Bloody good job too John thought.

Sherlock, however, was the definition of calm.

"I wasn't expecting you home until tomorrow." He remarked, gazing almost blankly at John. He didn't even bother to cover up, as John had seen it all before whilst patching him up after cases. Apparently John thought this was different though as he threw a blanket at Sherlock.

"Yeah, I can see that! So what? I was out and... and..." John didn't even know what to say, he was shocked, confused, and appalled. "Does this happen every time I'm out?!" He asked, forcing images of the two of them in other areas of the flat out of his mind. Mycroft shifted on the bed, making a move to get up, dressed, and leave. Sherlock stopped him with a hand on his shoulder and a shake of his head.

"No John, this is the first time Mycroft and I have taken this step in our relationship." He explained calmly.

"Relationship?! He's your brother Sherlock." John hissed, absolutely incredulous.

"Oddly enough I am in fact aware that Mycroft is my brother John. I fail to see how that makes any difference whatsoever." Sherlock stated, a little less calm now. Mycroft was getting more uncomfortable by the second, and Sherlock was becoming fearful that John would be able to convince him of how wrong this was. After all the effort it had taken him to convince his brother that it was so right.

"Fail to... you can't be serious? Sherlock, it's incest! It's just... wrong!" John stammered, unable to comprehend how anyone- even Sherlock- could be so socially inept. Mycroft sat up once again, pulling the covers tight around himself to avoid any further embarrassment.

"Brother, John's right. We shouldn't have-"

"No!" Sherlock leaped to his feet, pulling on his shorts in the hopes that John would take him more seriously. He spun to face his brother, silently pleading him to stay. Mycroft's eyes flicked between Sherlock and the door before he finally sagged back into the pillows, muttering about how wrong this was.

Sherlock then wheeled to face John, glaring dangerously. "You will not take this from me John." He snarled. "You're supposed to be my friend."

"I am your bloody friend!" John defended. "But he's your brother. How can you think this is okay? And you" he turned on Mycroft "you should know better. How could you allow this to happen? How could you do this to him?!" Mycroft's expression was a mix of shame and guilt.

"John I-"

"Mycroft! Don't you dare turn back on me now!" Sherlock yelled, his voice somehow both pleading and commanding. Mycroft instantly snapped his mouth shut, having never seen his brother quite so desperate. Once again Sherlock turned on John. "My brother has done nothing I didn't ask of him." He explained first of all, refusing to allow John to blame Mycroft for any of this. "So tell me John, why is this so... wrong?" He spat the word as though it left a foul taste in his mouth.

"Because he's your brother." John repeated for what felt like the hundredth time. Both of their voices were slightly lower now, more serious.

"And what does that mean exactly? We share the same parents, similar physical and personality traits, and we know each other better than anyone else ever will." Sherlock offered Mycroft a small smile before turning back to John. Mycroft didn't return the smile, fighting every instinct that told him to leave the room now.

"Yeah, yeah it means all of that I guess. And yeah you're supposed to be close, but as brothers Sherlock, not as... this." John waved his hands in their general direction, unsure quite how to describe what this was. And not really wanting to think about it too much.

"And why is that?" Sherlock queried as he advanced on John. "You still haven't given me a legitimate reason for why Mycroft and I can't be together. Whereas I can give you several as to why we should." He stopped a few inches away from John and folded his arms in front of his chest, waiting. John stared at him in disbelief, and Mycroft sat forward just a little.

"Him being your brotheris a legitimate reason Sherlock. It's wrong, it always has been, and it always will be." John attempted to explain. Mycroft sighed, finally standing.

"Once again John is right brother. We shouldn't have done this, and we certainly can't do it again." He shook his head as he pulled the covers tighter around himself, looking truly regretful as he stepped toward the door. Sherlock saw this an exploded with rage and fear.

"NO! He's not right! It's not a bloody reason!" He screamed, terrified that everything he had worked so hard for was falling down around him. Mycroft stilled by the door as Sherlock rounded on John, eyes ablaze with fury even as they shimmered with tears. "How could you?!" He bellowed, causing John to step back in shock.

"How-" He tried, but Sherlock cut him off.

"You're supposed to be my best friend, so why, why are you so determined to see me miserable?"

"Sherlock I'm not-"

"Yes you are!I was actually happy, and you've gone and taken that from me!" Sherlock's vice shook, his tears starting to fall despite his best effort. He didn't want to cry in front of John, but he couldn't stop himself. John made to move toward his friend, but Sherlock held up a hand and stumbled backward.

Mycroft was glued to the spot by the door, staring at his little brother. He was utterly torn. He wanted nothing more than to go to Sherlock, to hold him and kiss him, to make everything better. Yet he also knew that John had a point; what they were doing was so very wrong. Hell, it was illegal. So he stayed in his place, silently battling with himself while Sherlock continued to berate John through his tears.

"Mycroft made me truly happy, for the briefest period. He's the only one who has ever understood me, the one man I've ever loved. And you drove him away." Sherlock collapsed back on the bed, his head falling into his hands.

"Sherlock I-"

"I don't want to hear it John, just leave." Sherlock muttered. John had never seen Sherlock looking so broken. He gave him one last sad look before shoving passed Mycroft and leaving, just as the wave of guilt overtook him.