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(Y/N) leans against the door of her room, looking out into the living room where Sherlock was playing on the floor with little Rosie. If anyone from Scotland Yard -- or even his parents, for that matter -- walked into the flat right now, they’d never recognize him. She could hardly believe this was the same stoic, blunt, matter-of-facts man she’d fallen for a year or so ago. The smile on his face -- that absolutely beaming smile -- made him look like a completely different man.
Rosie brought that out of him. Sure, he smiled for (y/n) -- he had many different smiles for her that he gave no one else. But none like the one that instantly consumed his handsome features the instant he sees little Rosie Watson.
(Y/N) loved watching Sherlock and that smile play with her. It made her heart sing such a melodic tune it rivaled his violin playing on his happiest and most peaceful days.
“Are you going to join us?” Sherlock asked, patting the floor beside him.
Rosie, apparently agreeing with this idea, waddled over and seized her hand, bringing her back to where Sherlock waited for them with outstretched arms.
He pulled them into a group hug, gently kissing them on the cheek.
“I love you both so much,” he said over Rosie’s delighted giggles.
He released the little one so she could go get the purple lion plush toy she’d spotted over his shoulder.
Sherlock and (y/n) remained with their arms around each other. She leaned in for a quick kiss that he gladly returned.
“I want one,” he said quietly. His voice was shaky, barely audible, but certain.
“One what?” (y/n) asked, confused by his tone. She was used to him leaving out context to his requests due to his brain moving too fast for his voice to keep up. That tone, however, was new. Sherlock rarely hesitated.
He glanced at the toddler returning to them then looked back at (y/n), worlds of meaning echoing in his eyes.
Her heartbeat fluttered, but she had to reign it in. Test him to make absolutely certain he knew exactly what he was asking for.
“Are you sure? I know how much you love Rosie,” (y/n) replied, taking the odd lion she was being handed to hold onto while Rosie curled up in Sherlock’s lap with drooping lids, “but babies are far more work when they’re your own and not just around for a few hours on their parents’ date night. They cry, make messes, and need lots of attention. And are doing all of that and needing all of that attention for at least eighteen years.”
(Y/N) placed the lion in Rosie’s arms as Sherlock enveloped the little one in his arms and began rocking her to sleep.
“Yes, I know all of that, (y/n),” he whispered. He met her eyes, needing her to see how serious he was. This was no spur of the moment request -- he’d been thinking about this for a while now.
“Well,” she said with a playful smile that made his brow furrow slightly, trying to deduce what she was going to say, “do you also know that if we decide to have a child together, you will be stuck with me for the rest of your mortal life, Sherlock Holmes?”
Chuckling, he looked at her with the most loving expression he’d ever given her.
“Yes, I most certainly do.”