Hamish and angst! And don't worry, this one's a three-parter! Be sure to read the next two (Belittled, Beneficial) after this one.
After clamoring about in the kitchen, Sherlock stuck his head into the sitting room where John was helping Hamish with some homework.
"Have either of you seen the plate of kidney slices I left in the fridge?"
Hamish looked up, somewhat guiltily. "Sorry, father, I thought that was spoilt food, I threw it in the bin out back."
"You what? I needed that!"
"I'm sorry! Something smelt off in the refrigerator, I thought I'd tidy up so you or dad wouldn't have to." John reached out, patting his son's hand comfortingly.
"Sherlock, it's not a big deal. I'll get you some kidneys from Molly, you can start it over again tomorrow."
"You useless, idiotic child. You've ruined two weeks of work."
"Yeah, well you're a terrible excuse for a father. I don't care if it's bloody obvious my genetic material came from you, John's my only real dad." Hamish stormed up the stairs to his bedroom before even Sherlock could notice the tears welling up on his lashes. He reached the landing at the top of the steps and sat down heavily, wrapping his thin arms around his knees. Strains of shouting carried up from the kitchen.
"Most parents would kill to have such a well-mannered son who cleans up without being asked. For Christ's sake, Sherlock, he's just a boy!"