It is the opposite of a birthday present, and Sherlock doesn't baulk from saying so, throwing himself bodily over the small suitcase half-packed on Mycroft's bed. Mycroft simply lifts one limp, lanky arm just enough to slip another pair of clean socks into the case, then settles to sit on the bed, stroking a hand over Sherlock's curls.
"I must go back to school." Mycroft's tone is gentle, but not apologetic. Sherlock considers how quickly he would have to move in order to shove the suitcase off the bed and scatter the contents. This bag is not large enough for Sherlock to wedge himself inside, unlike the positively roomy luggage when his brother first left for Eton.
"But it's so dull!" Thumping his fists against the duvet, Sherlock ignores the hardback prodding him in the ribs. Novels from Mummy and Father are not interesting presents, nor indeed are the new underthings and socks. Sherlock had spent months reassembling the skeleton of the bat he'd found dead in the verbena behind the conservatory— ants had already taken care of some of the flesh when he found it, and careful boiling in the kitchen after everyone else was deep asleep finished the last of the messy bits. Then had come the paste, fishing line, and an old picture frame from one of the storage cupboards. It had been the best surprise, the only time Sherlock had ever managed to properly surprise his brother with a Christmas present, and Sherlock knows Mycroft wrapped it up in a jumper and tucked in the back of his closet even after Father had ordered it thrown away.
The possibility that it might have been moved to the suitcase suddenly occurs to Sherlock, and he rolls off to sprawl across the mattress instead, headbutting his brother in the podgy softness of his stomach. "Horribly, impossibly dull! You said so in your letters— even when you don't say the words, I know. You hate it just as much as me."
"Just as much as I," Mycroft corrects, earning another headbutt.
Blowing air out from his nostrils, Sherlock groans in a near-perfect imitation of Wally, the gardener's bull terrier. "You're going to miss my birthday."
"We had cake and presents today, Sherlock, and I promise I'll ring you tomorrow." His present from Mycroft had been a new book of sheet music, including some pieces that made Sherlock's fingers ache with anticipation of a challenge, and a bag of Sherbert Lemons. He didn't bother remembering any of the other gifts, and he had barely picked at the spongy yellow cake, smearing pale blue icing with his fork.
"Birthdays are terrible, and so are you," Sherlock announces, winding his arms around Mycroft's middle and squeezing too hard, until his brother wraps one arm around Sherlock's shoulders, the angle awkward, and squeezes back.