Sherlock and Mycroft do love each other. They are after all the only ones who truly understand each other. So when nobody's watching, they actually have a rather mundane bromance. (no holmescest!) They touch each other affectionately, when they have time they read books together and of course mock the author together. I can see Sherlock bringing his brother a cupcake cos he knows how much he likes it and really he should be allowed to stray from his diet every once in a while... Mycroft keeps Mummy off Sherlock's back and maybe he helps Sherlock figure out a clue to a case... Maybe Sherlock helps his brother with some paperwork cos he hates that, or maybe brushes lint off his suit without even thinking twice about it, and maybe Mycroft gently kneads Sherlock's neck when he notices his shirt is starting to irritate him... when they say goodbye and there's noone around, they share a hug, before Mycroft goes back to work or whatever.
I'd love to see that sort of thing. Normally they wouldn't touch if their lives depended on it, but I'd like to see them touch like it's the most normal thing for them.