"No Mycroft, anyone but her." Sherlock protested as Mycroft looked at him, the slightest suggestion of a smug smirk tweaking at the corners of his lips.

"It's too late brother, she is on her way and you can't stop it. The good Doctor saw fit to invite me to his upcoming nuptials, and she is to attend as my guest." Mycroft said, as he rose from the chair.

"Oh, and by the way Sherlock, she will be staying here with you." Sherlock spluttered and put down the violin.

"What do you mean she's staying here? Oh no, no, no she's not staying here."

"Who's staying here?" Asked John as he walked into the room.

"Ah Doctor Watson, you and Sherlock are to have a special visitor she'll be staying here for a while, well at least until she is able to find more suitable accommodation." John looked at Mycroft and saw an obvious smirk on his face.

"She? She who?" Asked John.

"My guest for your wedding celebration Doctor." Mycroft said as he made his way to the door.

"Don't forget Sherlock, play nice, I don't want to have to come and break you two up. Plus, you know she'll win." Mycroft smirked again causing Sherlock to stare daggers at him.

"I've already informed Mrs. Hudson that she will be arriving so get used to the fact." Mycroft said, opening the door.

"Doctor Watson, always a pleasure. And do enjoy your time with your guest." Before anything else could be said, Mycroft glided out of the door.

"Ok Sherlock, what's going on?" John asked as he sat down in his chair.

"Mycroft has invited her, why couldn't it be anyone but her?" Sherlock whined, putting his head in his hands.

"Sherlock, you are going to have to stop being so cryptic. Who is her?" John asked, starting to get annoyed by his friend's lack of an answer.

"(Y/n), that's who." Sherlock said from behind his hands.

"Sherlock, let's just presume that I have no idea what you're talking about shall we and will you tell me what the bloody hell is going on." The tone of John's voice made Sherlock raise his head.

"(Y/n) Holmes, or Puck as Mycroft calls her, my twin sister." Sherlock said, finally answering his friend's question.

John's eyes grew wide. "Wait! there's three of you? And the other one is a girl? And you're twins?"

"I don't understand what is so difficult for you to comprehend, yes there are three of us, yes (Y/n) is a girl, and yes she's my twin." Sherlock said with slight frustration in his voice.

"Why have you never told me about her before? What does she do? Where is she coming from?" John's curiosity was definitely peaked.

"(Y/n) and I are very different but very alike which has made our relationship difficult over the years. She has been an independent consultant for the behavioural sciences unit at the FBI headquarter in Quantico for a number of years. She primarily deals with serial killer cases and cases on violent sexual crime." Sherlock told John, trying to sound unimpressed at his twin's achievements.

"WOW! She sounds interesting." John stated, now he definitely couldn't wait to meet her.

"Please John, when she gets here don't encourage her, her ego is big enough as it is." Sherlock scolded.

"Her ego can't be bigger than yours!? It's impossible. Now this I have to see." John said, laughing out loud.

Two days later and there is a knock on the door of 221B Baker Street. Mrs. Hudson rushed out and opened it. Standing at the top of the steps was a young woman with short spiked bleached blonde hair, dark smoky eye makeup, dark red lips, dressed from head to foot in black, finished off with a long black coat that swept the floor.

"Hello dear. Can I help you?" Mrs. Hudson asked quizzically.

"Hi, my names (Y/n) Holmes, I believe Milly told you I was coming. You must be Mrs. Hudson?" She said putting her hand forward for the other woman to shake. The older lady looked at her with shock in her eyes.

"Oh, yes, hello dear. It's a pleasure to meet you, I'm sorry you're not quite what I was expecting." Mrs. Hudson said, reaching out to shake her hand.

"That's ok, I get that a lot." She said with a laugh.

"Is Sherly home?"

"Oh of course, please come in." Mrs. Hudson said opening the door wide as the young woman grabbed her bags and entered the residence.

"Sherlock, you have a guest dear." Mrs. Hudson called through the door, before she smiled at (Y/n) and made her way back down the stairs. (Y/n) could hear shuffling from the other side of the door, a few disgruntled grunts and the voices of two men involved in a brief argument. Slowly the door opened to reveal Sherlock who looked less than impressed to see her.

(Y/n) leaned against the door frame. "Hi Sherly, long time no see." (Y/n) said as Sherlock just stared at her blankly.

"I know Milly told you I was coming, aren't you going to ask me in?" Still no response.

"Nice to see you are as gregarious and pleasant as you always were." (Y/n) said sarcastically, grabbing her bags and pushing her way past him into the flat. As she entered the sitting room she was greeted by a smiling man.

"Hi, you must be (Y/n), I'm John Watson, it's nice to meet you." He said, holding out his hand for her to take.

"Hello John, it nice to meet you too, if you haven't worked it out yet, I'm the most attractive and intelligent of the Holmes." She chuckled.

"Milly told me all about you, congratulations on your upcoming wedding. The only problem is, he didn't tell me how cute you were." (Y/n) smiled, giving him a quick wink.

(Y/n) heard a groan from behind her. "Oh please (Y/n), you've only just got through the door and your flirting, it's so embarrassing." Sherlock said as he shut the door and flopped down into his chair. She smirked at him.

"It's not my fault Sherly. It's not every day you meet such an attractive doctor and an ex-army man to boot. What more could a girl ask for?" She said seductively to John who started glowing bright red.

She turned to look at Sherlock. "Aren't you pleased to see me Sherly? Doesn't your baby sister get a hug?"

"You're only 5 minutes younger than me, I hardly feel that constitutes you being able to call yourself my baby sister, we are twins."

Laughing at the irritation in his voice and just to ensure she tortured him a bit more she skipped over and sat on his lap giving him a big hug.

"Well John, I take it that my darling brothers have never mentioned me before?" She said pulling Sherlock in tighter to her side squeezing him ever so slightly.

"I'm afraid not (Y/n), I only heard about you two days ago when Mycroft mentioned you were coming." John said as he sat down in his chair across from Sherlock.

"That's ok John, I'm used to it. Sherly here never mentions me as he knows how much better I am at everything than he is, plus he gets embarrassed at my shows of affection. And, well, Milly is just Milly." She said, shrugging. Sherlock suddenly stood up and (Y/n) dropped to the floor with a thud.

"What do you mean you're better than me at everything? You are most certainly not (Y/n)." The indignation in his voice only served to push her further. She pushed herself up from the floor.

"Sherlock, of course I am. I play the violin better than you, I deduce better than you, we both know my IQ is higher than either yours or Milly's. And I am far cooler and more calculated than you; you have even begun to let sentiment into your life my dear brother." Sherlock looked at her strangely.

"That is ridiculous (Y/n), you know I believe that sentiment is a chemical defect found in the losing side." Sherlock said with a huff.

"Then how do you explain the presence of the dear doctor here? He is your friend Sherlock, and despite your outward signs of ambivalence towards him it is obvious that you care deeply for your best friend. You make allowances for him; you take him along on cases not just because you have an overriding urge to impress everyone but also because you trust him. The doctor is, or at least tries to be a calming influence on you even when you are cast adrift in your own mind. You have lost Sherlock; you have opened up your life to sentiment and you will always lose to me." (Y/n) said, crossing her arms over her chest.

"I'm sorry if my little speech made you feel uncomfortable doctor. I can tell that you are a good man and care for my brother otherwise you would not put up with him, and I appreciate what you do for him." (Y/n) said, giving John a small smile.

Before anyone could say anything, else Mycroft pushed the door open and walked in, stopping and staring at Sherlock and (Y/n).

"Sherlock, I thought I told you to be nice, have you upset my little Puck already?" Mycroft said as he walked over and kissed his sister on the cheek.

"Hello Milly, I think you'll find it is I that have upset Sherlock, my apologies."

Mycroft took her by the hands. "Well that's alright then." Mycroft said smirking at Sherlock.

"I don't mind in the slightest if you upset him." Mycroft said, uncharacteristically chuckling at his own comment.

"I am so glad that you accepted my invitation for the wedding Puck, and for the job." Mycroft said.

"What job?" Sherlock asked, looking intently at his siblings.

"My dearest Puck here is going to work with her majesty's government as liaison with New Scotland Yard. And that is why she is staying with you, until she can find appropriate accommodation. She is moving back to London; it's been arranged for some time."

John couldn't help but laugh at the horrified look on his friend's face.

"You mean I will be forced to put up with both of you? This is completely unacceptable." Sherlock grumbled.

Suddenly there was a knock on the door. "Hopefully this is the man I was waiting for." Mycroft said as he left (Y/n) to invite in the new visitor.

"Ah, good, there you are, come in Lestrade." Mycroft said, signalling for the man to enter the flat, as he did so he shook John's hand.

"Lestrade, I would like to introduce you to my sister (Y/n) Holmes." Mycroft said, beckoning for her to come forward. She walked up, taking the man's hand in hers, as he stared intently at her, a large smile appearing on both their faces.

Mycroft continued. "(Y/n), this is........."

"This is Detective Inspector Greg Lestrade of New Scotland Yard." She said, interrupting Mycroft.

Lestrade looked at her. "How did you deduce that?" He asked looking slightly shocked.

"I didn't deduce it at all detective, it's called a computer and the internet, I knew Milly would want to introduce me to the man I would be working with at Scotland Yard, so I just looked you up." She said, smiling at him, making Lestrade chuckle.

"I can deduce a few things about you if you like though?" She said sweetly, seeing his slight look of discomfort.

"Don't worry detective, unlike Sherlock I don't like airing everyone's deepest darkest secrets in public." She said with a wink, as a pink flush came to his cheeks.

"But I do like the fact that you are no longer married though Detective, it means that I have someone to dance with at the wedding, when my brothers refuse, that's if it wouldn't upset your date?"

Greg shook his head. "No, I'm afraid I'll be desperate and dateless." He said.

(Y/n) had to admit that the detective was quite attractive, he was slightly older and that salt and pepper hair, his bright smile, and beautiful brown eyes were doing terrible things to the butterflies in her stomach.

As the two stood there still hand in hand, looking into each other's eyes, they were interrupted by an irritated cough from Sherlock.

"When you two have quite finished." He scolded.

(Y/n) turned her head and scowled at Sherlock.

"If you aren't busy Greg, how do you fancy showing a girl where to get a good cup of coffee in this city? If you guys are anything like the cops in the States, you can sniff out a good cup of jo a mile away." (Y/n) said with a giggle.

Greg looked at the incredulous looks on the faces of her brothers behind her, a huge grin growing on his face.

"Ms. Holmes it would be my pleasure." Greg said, holding out his arm for her to take, before leading her out of the door.

"Don't wait up boys." (Y/n) called out as Greg escorted her down the stairs, and out into Baker Street.

As the pair walked down the street, arm in arm, chatting happily; (Y/n) couldn't help but think that a move back to London might be the best thing she ever did.