Seventeen days had passed since Hamish Hatherly had come to live at 221B Baker st. He had begun playing violin at the level of somebody who had been playing for five years or more, and Sherlock was starting to teach him John's song. On the eighteenth day of Hamish's residence, Lestrade came by. "Oh, hey, Greg, what's up?" Said John, emerging from the kitchen where he had been making blueberry muffins ("Yours favourite!" according to Hamish). Sherlock simply looked up and nodded before returning to Hamish's maths (he was teaching him advanced quadratics, quite successfully).
"I'm just checking in... Can I have a word with you and Sherlock?" "Yeah, of course. Sherlock, can you come to the kitchen for a minute?" Sherlock gave Hamish a few final instructions before joining them. "If you're asking about Hamish's parents' murder, I'm suspecting that the murderer wore a Japanese-style Noh mask. As for his connection to Mrs. Hatherly, I'd say to check for any affiliation with gangs or crime syndicates. It's unlikely that he was a past lover due to the lack of damage to her husband, but that's also possible..."
"Actually, I was here about Hamish. We haven't found any relatives, and none of his parents' friends are interested in taking him. Apparently his intelligence scares them. Is he getting on well here, or would you want to find him a home somewhere else?" "He's getting on wonderfully here, I'd like to keep him around... Sherlock?" "Of course we'll keep him. He's a lot like me, though, so we need to make sure he socializes well. How do we apply for custody?"
"I can bring by the forms tomorrow, but I'm sure that Mycroft would get it sorted out much more quickly..." Lestrade blushed slightly. "Yes, how is that going? I wouldn't have thought, but I suppose it would be good for both of you..." Sherlock trailed off. "Wait, what? What's going on?" Asked a very confused John. "It would appear that my brother has deduced my current relationship with Gregory," came Mycroft's voice from the door. "As for Hamish," he continued, "I saw to it that custody over him went to the two of you. This is him, I suppose? Nice to meet you, Hamish, my name is Mycroft, I suppose that I'm a bit like your uncle now."
"'Lo, Mycroft. Go away no, need to focus." "Okay. Are you learning maths?" "Yes, Sher is teaching me." "Quadratic functions?" "Yes. Go away now, Mycroft," said Hamish in a very Holmesian way with a hand wave that made him look even more like Sherlock than usual. Mycroft turned to the kitchen. "He's already so much like you, dear brother," he said with a pained smile. "I'm taking precautions," Sherlock replied.
Just then, the timer for the muffins went off. "Precautions against what, exactly?" John asked as he checked the muffins for done-ness and pulled them out, then walked back to the group and hugged Sherlock from behind, not exactly caring what Mycroft and Lestrade thought. "It would seem that Sherlock is concerned that Hamish, like him and myself, will develop a social disorder or phobia based on how people of average intelligence will treat him. You may have already noticed a difference in how he talks to you or Mrs. Hudson compared to how he talks to Sherlock or myself.
"It's a defence mechanism of sorts. Sherlock and, to a lesser extent, myself used it as well as children, to stop people from being scared or nervous. You'll need to give him plenty of attention, John, make him feel loved or he could end up worse than the two of us, especially with what he's been through." "Yea, about that. He's already showing signs of PTSD. Not just the nightmares, he'd get those regardless, but his right arm has a tremor and he has flashbacks. I know the signs, I still display them, but I have no idea how to help him with this."
Mycroft thought for a moment before concluding, "I'm not sure how much can be done for a child his age, though it was a good job that you got him into a familiar environment after the incident, Gregory, or it may have been much worse." "Well yes, and tea always helps. Something about the tannin..." At which point, Hamish came in to show Sherlock his work. "Look, father! I finished!" Sherlock startled a bit at the new endearment and crouched to look at Hamish. "Hamish, what did you just call me?"
"Father. Is that not good? I heard you talking. You and John are my parents now, right? So you're father and John is dad. I can just call you by your names if you'd prefer, though." Sherlock scooped Hamish up gently, pressing a kiss to the boy's temple and smiling. John wrapped his arms around the two of them, smiling gently at them. Greg and Mycroft shared a look and quietly ducked out, leaving the small family to themselves.