From a Tumblr prompt.

Edison Holmes had his best concentration face on. His brow scrunched together and eyes piercing in their gaze towards his mother. Molly Hooper was used to that look, seeing as the family of four she belonged to had three fast paced, inquisitive minds.

Edi had never much taken after his father, apart from that look; much like his sister they had 'borrowed Daddy's deducing face'. He always found it harder to deduce than his sister, but the small age gap had aided that divide. Ariana was at school today, already somewhat fast tracked at the age of six. Edi was at home, still in the half days of reception class.

"Can we name it after a scientist like me?" His face had dropped the slight confusion, and now, like most days Edison had began the task of setting up his well loved 'Thomas the Tank Engine' train set, across 221b's floor. He couldn't let his Daddy down, even with his curiosity of his Mummy's news bubbling over, every night the tracks are disassembled, and (case dependent) every afternoon Edison and Sherlock Holmes will create a new and exciting route for Edi's many trains, when Daddy wasn't home yet, it was the three year olds job to start on the adventure.

"What's that sweetheart?" Molly had been in the kitchen, her ritual up so far undisturbed by Edison's stony faced concentration aimed in her direction, tonight's dinner had to be in the oven so when she picks up Ari from school, Sherlock permitting, the family can each straight away, seeing as Ari's clubs always ran late.

"Well, Ariana's name is strange like Daddy's."

"Yes, I suppose. But not in a bad way I should hope."

"Oh no." He shook his head adamantly, which Molly couldn't help but find the most adorable and hilarious endeavor. "Ari, has the prettiest name in all the world. Like you Mummy, but it's strange too, like Daddy."

"What's this all about Edi?" Molly did now halt her chopping, the peppers neatly sliced on the chopping board, she knelt down a little to face the little boy, he was still enraptured by the wooden tracks that sat in front of his, his still somewhat pudgy hands connecting one to another, but the advantages to having such clever parents and such a fantastic brain meant talking and doing were not a problem.

"Well, you have to name it something. My name is normaler than Daddy's and Ari's like yours, but I'm named after a scientist. Maybe the new baby could have a special name that's a scientist's and strange, or pretty, or both." He hadn't looked at Molly much when he was talking, enough though to notice the shock that coloured Molly's expression.

"New baby?"

"Oh, yes. Has Daddy not told you yet? Or does Daddy not know? Shall I tell him and Ariana. They'll be proud I deduced it all on my own." Edison had noticed how his Mummy had started to look more cuddly, how she looked pale in the morning as if she had tummy-ache, and when she seemed to cry more than necessary at Ariana's princess films. Ari and Daddy had told him what Mummy was like when he was in her belly and the clues all fitted. Molly beamed at her clever little man, he was his father's son as much as he was his mother's. Gaining her strong heart from a young age, always in want of a cuddle, always aware of his parents feelings, but oh so very clever.

Of course he had been around Molly more, seeing her and studying her more than Sherlock or Ariana had the chance to. Still it was her body and she had only figured it out two days ago. She was going to tell Sherlock tonight (having not seen him since she'd discovered it herself), news of a new little bundle of trouble, and then when the coast was a little more clear break the news to the children of their new partner in crime. Looks like Edi's beat me to it.

"Only I knew sweetie. Daddy was away when I found out. They will be so proud of you, I'm so proud of you. Shall we tell them together? After tea." Her emotions already a little wild from the extra hormones rushing through her bloodstream, Molly had to actively prevent the happy tears that would have easily accompanied her proud smile. Edi got up to go give his Mum a cuddle, squeezing her until he knew that she wouldn't cry anymore, giving her a loud kiss on the cheek.

"Yes please. Thank you Mummy." He turned back to his trains, waiting for Sherlock and Ariana to get home, the quicker the better; he had important things to tell them.

—-

Edi wriggled his way through dinner. Although excited about the news, Molly was aware of a need to maintain routine and order in what was once such a disorderly household, (that still on face value appeared to be such).

When Sherlock dropped himself down on the sofa, case solved, ready for his marathon sleep, he felt a gentle pudding at his arm. Edison had dragged his sister into the sitting room, his mother in tow and was now attempting to garner his father's attention. Easily done it seemed as Sherlock smiled, opening his eyes from his elongated blink. And ready to address whatever pressing matter seemed to be at hand, secretly hoping it had something to do with Thomas and the other engines.

In the sweetest fashion, although not what he was aiming for, Edi cleared his throat to begin his little speech, not allowing his Molly a word in edge ways he began. "I have some very important news for everyone. I deduced something all on my own today, Mummy is going to have a baby," considering it being the focal point of the news Edi skimmed over that part quickly, prompting a stifled giggle from his mum, "and I am going to call it something that is pretty like Araina, strange like Daddy, and a scientist like Mummy. I looked in one of my books and I think Marie."

Molly was about to argue that the name was quite normal, but was swooped up into her husband's arms, a kiss that was interspersed by giddy smiles occupying her lips, Sherlock hands splayed across the soft and soon to be growing curve of her stomach. Each kiss was punctuated by happy revelations and need of conformation. To his 'really?' Molly could only nod enthusiastically.

Ariana and Little Edison Holmes, turned up their noses, at the sight before them, in a way that resembled their father to a tee. "Daddy, Mummy. Stop it."