I dwell in Asgard

Mycroft hates how "awful" Sherlock's handwriting is but once Sherlock has a civilian write something down for him, sign it off as SH and has it sent to Mycroft and Mycroft calls all of MI5 and 6 and the CIA because THAT'S NOT HIS BABY BROTHER BUT IT'S HIS CODE SOMETHING IS VERY VERY WRONG.

Female colleague : They can be a handful at that age.

Mycroft : Yes.

Female colleague : I love children. How old is he?

Mycroft : Nineteen.

Mycroft tells him to stop, but Sherlock replies that he's being a hypocrite, because he's learned the word from him. Mycroft is confused, and Sherlock informs him that he once heard him saying the word back when he was four.

Sherlock may have deleted the solar system from his brain, but he has a perfect memory of the one instance when he heard eleven year old Mycroft saying fuck.

Sherlock: *develops a perfect memory in regards to his brother and copies literally everything*

Mycroft: Oh no HE'S FOLLOWING EVERYTHING INCLUDING THE STUFF I CAN'T I HAVE TO BE GOOD ALL THE TIME NOW

9 year old Mycroft scolds Sherlock for throwing a tantrum when the au pair girl tries to dress him.

It turns out that Sherlock saw Mycroft - who is usually polite to the au pair girl - being a drama queen about the clothes she had laid out for him on the previous morning (Mycroft : "I can’t possibly wear this sweater with these trousers!").

Sherlock to anyone dead or alive: My brother was just made perfect see everything he can don and look what he's taught me and—

Meanwhile Mycroft to anyone dead or alive somewhere else: My brother is absolutely wonderful look how much he's helped me without him I'd never even be here he's so perfect and he's mine and look how much he helps people and—

Mycroft and Sherlock to each other: Urgh you're so annoying could you stop?!