Mycroft telling Sherlock it says gullible on the ceiling and he falls for it every time
Sherlock flicking Mycroft’s ear when ever he falls asleep while reading a book on the sofa
Mycroft pointing at something on Sherlock’s chest and when he looks down he flicks his nose
Sherlock telling Mycroft he’s not stupid and Mycroft saying hello not stupid, I’m Mycroft
Sherlock and Mycroft having week long prank wars until there mum gets so irritated she confiscates their books
Mycroft teasing Sherlock about how he’s smaller than him
Sherlock and Mycroft having water fights on hot days
Sherlock having a night mare and going straight to Mycroft’s room because he know he’ll help
Mycroft making Sherlock cocoa and reading him a story
Sherlock getting picked up from school by Mycroft, who holds his hand while crossing roads and teaches him deduction
Adult Sherlock and Mycroft pretending to hate each other in front of other people, and smirking at each other from opposite sides of the room because they know it’s pretend