A/N: Hello chaps! I know I have another story on the go, but I just couldn't wait to share this with you! I would like to thank A genius says for giving me the prompt for this story. I hope to explore the development in Sherlock and Mycroft's relationship, so expect lots of brotherly love! I hope you enjoy, and I apologise for any issues in characterisation.

If you have time to review then I would love to hear from you :) xx

Against Their Nanny

When most young children received a new sibling they would get overly excited and want to play with them instantly, not understanding that the tiny beings needed some time to develop first. Mycroft Holmes was not most children, and so when his baby brother Sherlock came along it was Mycroft's curiosity over the tiny boy which meant he did not mind just standing and watching his brother rather than trying to interact with him too much.

Mycroft had never met a human so small before, and so he fondly observed the way Sherlock grew to babble to himself, to eventually sit up and then crawl. Mycroft would spend many an evening in his brother's nursery, sat in the chair beside Sherlock's crib, taking notes as the baby giggled at getting his own limbs in a tangled mess. He only ever smiled or giggled when Mycroft was around, and the older boy wondered why.

"It's because he loves his big brother" Mummy would tell him with a smile whenever Mycroft asked about it.

Love was a complicated subject, Mycroft found. He thought love was only reserved for partners like Mummy and Daddy, but he found he did indeed love Sherlock, and he was glad to know Sherlock loved him.

It was true Mycroft did spend more time with Sherlock than most. Daddy was always working away or in his office, and Mummy herself was usually at work or with friends. That typically left Sherlock with the nanny, Elizabeth, for most of the day until Mycroft got home from school.

Elizabeth was a miserable old creature and Mycroft did not at all know what Mummy saw in her, but Sherlock always seemed happy to get away from her when Mycroft finally came home. The older boy would usually go into the nursery to find Elizabeth rocking Sherlock and trying to get him to sleep, but he would be fighting and she would verbally scold him. Mycroft did not like the feeling that gave him, and after doing some research he found said feeling was the need to protect his baby brother from people he clearly did not like.

As soon as Sherlock saw Mycroft he would stop fussing and instead reach out his tiny arms, gripping his hands open and closed and whimper slightly to show he would rather be held by Mycroft. Elizabeth would just sigh, clearly not caring, and dump Sherlock in Mycroft's arms on her way out. Again, it was lucky Mycroft was no regular seven year old, and so knew fairly well how to treat his little brother after extensive research, but it was still very irresponsible for Elizabeth to leave them.

When Sherlock was safely in Mycroft's arms, he would gurgle happily to himself and rest his head on his brother's chest, his little hands gripping Mycroft's shirt. It made Mycroft feel warm inside…happiness, he thought it was. He had been so utterly lonely before Sherlock was born, and now he was going to teach his brother everything he knew so he could finally have someone to talk to with peer intellect, and saw the world how he did.

One afternoon when Sherlock was 15 months old and Mycroft just turned 8, the older brother arrived home from school to find Elizabeth in the nursery talking to one of the maids rather heatedly about Sherlock, who sat blissfully unaware in his playpen stacking his toy blocks.

"There is something wrong with that child" Elizabeth said, and the maid tried her best to ignore her and carry on cleaning. "Surely he should be walking by now, her barely even crawls! And he should certainly be beginning to speak, but he never much as utters a sound! I'm telling you, he's not right"

Mycroft's eyes widened as he listened in from the door outside; how dare she insult his brother like that, he was just a baby! It was true, Sherlock barely cried – which Mycroft could safely say was a good thing - and he did not make much noise when anyone else was around, but he always made happy babbling noises when he was with Mycroft. Clearly only he knew the real Sherlock even at this tender age. It was also true he had not started to walk yet, but all babies developed at different rates – Mycroft had studied it extensively.

The maid just hummed along uncaringly to Elizabeth's cruel accusations and then turned to leave. Mycroft quickly ducked out of sight and waited until she had gone before going into the room and marching right up to Elizabeth who had taken to slouching in the reading chair and lazily flicking through a magazine.

"There is nothing wrong with Sherlock!" Mycroft said adamantly as he stomped his foot on the ground. "He's just taking his time to…"

"Were you eavesdropping?" Elizabeth asked angrily as she folded the magazine away and stood up to her full height, but Mycroft was not scared. "I shall tell your mother!"

"And I shall tell her what you said about Sherlock" Mycroft retaliated, folding his arms across his chest to express his obstinacy.

"Oh, and who do you think she'll believe?" Elizabeth said snidely as she folded her own arms "The loyal woman who has worked for since before you were born, or a seven year old prone to telling lies"

"I'm her son!" Mycroft said; surely Mummy would choose to believe him…

"You're too mouthy for your own good, boy!" Elizabeth reprimanded "And the fact you are her son, I'm afraid, doesn't really count in this world. Adults listen to adults, not children who always think they know best"

"I am not most children" Mycroft retorted with narrowed eyes.

Elizabeth smirked "Neither is your brother, probably why he's so slow…"

"Don't talk about him like that, he's baby!" Mycroft continued to defend his brother, who at this point was sat watching them with wide unblinking eyes.

"Oh, I've had enough of this" Elizabeth said waving her hand dismissively. "You two are really not worth the trouble, ungrateful brat! I'll be having words with your mother" and with that, she stormed out the room.

Mycroft immediately hurried over to Sherlock who was starting to look upset by the loud shouting. As soon as the older Holmes picked his brother up out of the pen Sherlock nuzzled into his neck and Mycroft could feel the hot tears.

"Hey, it's alright" Mycroft soothed as he rubbed Sherlock's back and rocked him a little. "I won't shout anymore, I promise"

Sherlock sniffed and looked up at his brother, rubbing his eyes. Mycroft felt sad that Elizabeth could even think such horrible thoughts about his innocent little brother.

"Don't listen to anything that old bat says Sherlock, I already know you're special, but in a good way" Mycroft said reassuringly. "We'll just have to prove her wrong!" he said with an enthusiastic smile and Sherlock giggled – he liked it when Mycroft smiled.

"I'm going to teach you to walk" Mycroft said seriously as he placed Sherlock on the floor "Walk, see, like this" he said taking some purposeful strides up and down the room and Sherlock's eyes followed him in what appeared to be concentration. "Think you can do that?" Mycroft asked and Sherlock just blinked blankly. Mycroft sighed but still had a small smile on his face; this was going to be hard work.

"Okay, this time for sure" Mycroft said reassuringly as he placed Sherlock's tiny hands on the seat of the chair so he could steady himself on his still wobbly legs.

They had spent the last three days working on Sherlock's walking. It was the school holidays so Mycroft was able to spend all day with Sherlock, and also luckily Mummy and Daddy were away so Elizabeth had not had chance to talk to them yet.

Mycroft had started by hoisting Sherlock up onto his feet and slowly walking his little brother around the room whilst holding onto his chubby little hands. Sherlock was very dubious at first, his legs would eventually wobble and he would stumble, but Mycroft was always there to catch him we he fell. Eventually, Sherlock grew more confident after watching Mycroft and gurgled happily to himself when walking around with Mycroft's help.

However then, Mycroft had tried to get Sherlock to walk on his own and the little boy had hated it. The first time Mycroft let go of him Sherlock had been so scared he had starting crying right away and Mycroft had to cuddle him and 'hush' him for a good five minutes.

"It's alright, Sherlock" he had said whilst running his hand through the little boy's curls. "I won't let you fall. I'll never let you fall, not really, I promise" if only Mycroft had known the prominence of those words in the years to come.

"Come on, I know you can do this" Mycroft had said encouragingly as he once again stood up, still holding Sherlock's hands.

That was when he'd taken Sherlock over to the chair to prop him up and then Mycroft let go once more. Sherlock craned his head around as Mycroft moved away, and the older Holmes could see the tears once again welling in his little brother's eyes.

"Ssh, it's alright, I'm right here" Mycroft said as he knelt down just a few feet away and waited with open arms. Sherlock whimpered, but Mycroft knew he was so close. "Come on, come to me Sherlock, I know you can" he said, opening his arm's wide and beckoning the little boy forward with his hands.

Sherlock very cautiously turned all the way around, letting go of the chair and sticking his arms out for balance. He wobbled a little, and Mycroft got ready to lunge forward and catch him, but Sherlock recovered himself and placed his first foot forward.

Mycroft grinned widely "Yes! That's it Sherlock, I'm right here" he continued to encourage.

Sherlock moved his other foot forward; his first step on his own. Mycroft smiled proudly. Very carefully, and systematically, Sherlock slowly managed to move his way forward. The closer he got to Mycroft, the more Sherlock smiled and giggled to himself. Mycroft started laughing too, seeing how pleased his brother was with himself.

Eventually, Sherlock took the last big step and stumbled into Mycroft's arms. Mycroft picked Sherlock up and spun him around excitedly.

"You did it, you did it, Sherlock!" Mycroft said happily "I knew you could do it, I'm so proud of you" he hugged his brother close and Sherlock nuzzled into Mycroft's neck once more. "Just wait until we show Mummy, and rub it Elizabeth's stupid face" Mycroft added excitedly. "Come on, let's keep practising"

It was two days later – Sherlock was exceling by then, so Mycroft knew he was certainly a Holmes – when Violet and Siger Holmes finally arrived home. Unfortunately for the boys, Elizabeth managed to get to Violet first and told her about her 'trouble' with Mycroft the week before. Violet went to the nursery ready to give her son a stern talking to, Elizabeth in tow, but Violet stopped when she opened by the door, taken by surprise at the scene before her.

Mycroft was knelt down at one side of the room, arms wide opened, whilst Sherlock was making his way towards his older brother – albeit on wobbly legs – but he was actually taking some confident steps.

"Oh, darling!" Violet cried happily as she went into the room and swept Sherlock up into her arms "You can walk, oh I'm so pleased, well done!" She planted a wet kiss on Sherlock's cheek ignoring the fact he was already fussing to be put down.

"I taught him, Mummy" Mycroft said proudly as he looked smugly at Elizabeth who was stood in the door, eyes wide in shock. "He's getting really good"

"Well done, Myc" Violet said as she knelt down with Sherlock to hug her other son too – apparently any chance of a scolding had gone out of the window, much to Elizabeth's dismay.

Sherlock was still squirming and fussing in his mother's grasp until he suddenly cried out "Mycof!"

Violet and Mycroft both looked at the little boy, surprised.

"What did you say?" Mycroft asked "Did you say my name?"

Sherlock was holding his arms out, opening and closing his hands in Mycroft's direction "Mycof!" he said again insistently.

Violet wordlessly handed Sherlock to his brother and the little boy settled, resting his head against Mycroft's chest and sighing, a content smile on his face.

"His first word" Mycroft said "Did you hear that, Mummy? Sherlock's first word was my name!"

"Yes darling, I heard" Violet said proudly as she wiped a tear from her eye "You're a very good big brother Mycroft, and Sherlock clearly loves you very much"

"I love him too" Mycroft said with a smile as he looked at the little boy now asleep on his shoulder. He then looked over at Elizabeth who had been frozen in the door speechless the whole time. "My brother is a genius" he said with a smug look at her.

Elizabeth closed her gaping mouth and promptly stomped away – embarrassed by a seven year old and his baby brother! Mycroft stuck his tongue out at her back as she left – it was okay to be childish sometimes he supposed.