"Mycroft, for the last time, sex doesn't alarm me." Sherlock sighed. They were discussing a case and of course the older Holmes just haaaad to start teasing his younger brother.
"How would you know?" Mycroft countered with a smirk. He was quite smug about his response, sure he had caught Sherlock on his tail. John took another sip of tea and joined the battle of the wits for the first time.
"Well he seemed to know an awful lot about it last night." He took another sip and his face changed, as if he had just remembered something. "Oh, and this morning." Mycroft felt the smirk slowly start to slide off his face as he realized what John was saying.
"Twice last night if I recall correctly." Sherlock added mildly. Mycroft's lips sank into a frown and parted slightly as he was about to say something. Then he seemed to think about what he was going to say and closed his mouth.
"Oh yes… I almost forgot about that."
"Forgot? How could you forget my awe inspiring knowledge?"
"Well when your awe inspiring knowledge happened twice and the morning after and your backside hurts like the Dickens and your mouth is sore then your memory tends to lapse slightly."
"Your backside hurts?" Sherlock asked incredulously. "I couldn't put my trousers on this morning."
"Oh is that why you're in a sheet? I thought you were just lazy and didn't want to put clothes on. He sleeps naked you know." John said, directing the last part at Mycroft.
"Yes I know…" Mycroft said, slightly shell shocked and not sure how to deal with it.
"I used to go to his room whenever I had a nightmare." Sherlock elaborated.
"I bet that was… interesting?" John said, posing an implied question at the end. One of his eyebrows rose in the begins of suspicion and Sherlock shrugged.
"If you call Mycroft trying to shove a sobbing and naked 7 year old out of his room interesting then yes. It was interesting."
"So… you two are…" Mycroft trailed off, gesturing helplessly at the two men.
"Having sex? Together? Dating? Making love? Fucking? All of the above." Sherlock said then took John's arm and glanced at the watch on his wrist before standing. "Come along John, we have a client to meet." John set his tea down and stood as he glanced at his watch as well.
"Your right. Well it was nice seeing you Mycroft, I'm sure you have a lot to think about so we'll be taking our leave." With that the two lovers left a very shell-shocked Mycroft to sit and stew over the all the revelations that he had.