Sherlock is sick of Mycroft nosing in his business then one day Mycroft stops by 221B preaching.
Finally Sherlock is fed up so decides to kick him out of his flat by telling him what he exactly did with John the other night. Very Sherlock knows this is the only way.
At first Mycroft copes with it pretty well saying: Stop, Sherlock. Mummy will be very upset if she blah blah blah
Then Sherlock starts telling him very very private stuff and eventually Mycroft starts freaking out.
"Sherlock! Stop! Don't make me beg! Okay. I'm leaving. I said I'm leaving!" then he practically runs off leaving his umbrella behind... And all the while John is there, watching the whole scene blushing and shaking furiously.

Basically what I want is: Sherlock tells Mycroft his sex life in detail to kick him out of his flat while John is also in present.

OK, so that was the prompt on the LJ community thing. This is what I came up with...

I don't own sherlock.

"Oh god Mycroft, what I get up to in my spare time is none of your business!" Sherlock yelled at his older brother.

"Come now Sherlock, you know I'm only telling you the truth. Not big enough to hear it?"

"You know as well as I do that you're just trying to wind me up!"

"It's working though isn't it?"

"What is going on in here!" John yelled. The two brothers stopped to look at the ex-army officer that just walked in through the door, Tesco bags in hand.

"I was just telling Sherlock how, if he doesn't get his act together, he's never, ever going to find himself a boyfriend. Poor mummy will be disappointed so," Mycroft explained turning to look pointedly at Sherlock.

"Just leave Mycroft," Said John.

"No."

"Why not?"

"Because you want me to," He laughed and sat down in Sherlock's chair. Sherlock's chair. Now he'd done it.

"I'll have you find I do have a boyfriend, actually!" Sherlock yelled. Mycroft stood up.

"Oh really? Now tell me, what's this boyfriend of yours' name hmm? Bob? Dave?"

"John."

"Sherlock, I don't think…" Mycroft was starring at John, who was subsequently blushing violently and rambling nonsense.

"Oh yes, I'm sure. You and the doctor seem so very… loved up,"

"Quite,"

"Go on then, enlighten me… how long has this been going on?"

"Two months, four days, six hours and, say, 20 minutes,"

"Sherlock!" John's mouth kept moving but no words came out. He stood at the back of the room, forgotten, mouth opening and closing, making no smirked. He didn't believe it even for a second.

"Well, mummy will be pleased to hear about this!"

"No! I promised John I wouldn't tell anyone, so you can't either!" Sherlock yelled, as Mycroft took his phone from his pocket,

"Of course you did," He said, smug grin on his face as if to say 'I'm not stupid'.

"It's true. Want to hear what we did last night?"

"I'm sure I would little brother!"

"We were watching telly, something rather mundane, but John likes it, so we had it on. Then we began kissing. And it was very nice thank you very much,"

"Oh I'm sure it was, do tell, what happened after the 'kissing'?"

"Sherlock… don't…" John had found his voice, but went unnoticed as Sherlock carried on talking.

"Well, he does this amazing good thing where he kisses all down my neck. It's all rather hot and steamy."

"Oh it sounds it! And I totally believe this all happened."

Sherlock had had just about enough of his annoying older brother and his mocking tone. In fact, he'd had enough of his brother full stop. He flipped.

"Last night, John and I went into his room and fucked. Rather hard. We were naked and sweaty and it all lasted for the best part of three hours. He had his hands in my hair and was screaming my name. His dick is huge and I'm sure you are more than a little jealous of me, seeing as we do this most nights a week. There was cum everywhere, and when I say everywhere I mean everywhere. Do you know the good thing about army men Mycroft? The stamina! It's incredible, and the best part is he's been all mine for two months, four days, six hours and, around, 30 minutes!"

Everyone was silent. The only noise was Sherlock's heavy breathing, after loosing so much oxygen from his considerably long rant. John had practically turned into a tomato, eyes big, mouth wide open. He slid backwards slowly until he'd totally left the room and entered the kitchen, pushing himself up against the wall, admittedly hiding from Sherlock's stunned brother.

"Oh." Was all Mycroft could say. After he'd caught his breath he carried on, "Yes so um… I should really be going. I'll tell mummy you're doing alright then… um, yes… ur, bye." And he basically ran from the apartment.

"Well I think that showed him… John?"

Mrs Hudson had been sat in her living room, sipping tea as she listened to the whole conversation.

"Knew it!"