When Q was little, he assumed that Twelfth Night was simply another word for 'Sherlock's birthday', as though he got a special name for his, because that's the sort of thing he'd do. It didn't even seem odd that Shakespeare had written a play about it.
Yes, that's Sherlock all over, and I can see a little brother (an admiring little brother?) just accepting that Sherlock Is That Special.

he had a sudden fierce longing for when he was little and everyone was both alive and legally alive, and Christmas happened on Christmas, and things weren't as complicated
Only this family!

I'm starting to worry that when I finally get to Skyfall, I will be disappointed in Q because he will be less than you have made him! And I do mean "finally." Brilliant Husband has now announced that I really need to see Quantum of Solace and Casino Royale before I can watch Skyfall. I should have just gone with him to the theater!