Sherlock's brain moves slower than usual right now, whilst he's sick. He rewinds to a time when his brother looked the way he does now, though it's not too long ago. Five years? Maybe a little less. Time is doing strange things at the moment. But judging from the state of him Mycroft is still doing his active service, so Sherlock is either still living with their parents or he's only just moved to London.
And honestly, Sherlock is going to make the tea but his big brother is using that intuition he has that Sherlock lacks that tells him when he's needed. Oddly, Mycroft always knows. He pops up when Sherlock is feeling at his shittiest and he makes things better in his own way. He turns up when Sherlock is ebbing and cracking and on the edge and distracts him. He offers Sherlock the odd, comforting things that only he knows because he's raised Sherlock.
Sherlock slinks onto the sofa again and watches his brother move around the kitchen.
"Did you just arrive? You can borrow some of my clothes. You look...disheveled."