I was asked to continue this story so I have written Sherlock's sorting with a couple references to His Last Vows content so ye be warned!
Sherlock's sorting
William Sherlock Scott Holmes stood in front of the teachers table in the Great Hall of Hogwarts School of Witchcraft and Wizardry waiting with the other first years for his name to be called. He briefly turned to the Ravenclaw table and caught sight of his brother. The smallest trace of a smile crossed Mycroft's face as he nodded at the 11 year old. As the boy turned back to the front he smirked. Mycroft was expecting him to be put in Ravenclaw, that wasn't going to happen.
"Holmes, William." This was it, he was going to spite Mycroft once and for all! He was going to avenge Redbeard!
Sherlock approached the three legged stole and sat down. The Sorting hat was placed on his head.
So young Mr Holmes, quite the Ravenclaw aren't you?
'No,' Sherlock thought. 'That's my brother.' The word brother was spat by the boy's inner voice.
Well, we'll have to see about that, quite a Slytherin as well aren't you. I see you would so anything to achieve your means, am I right? But you are very intelligent, more so than your brother in some respects my dear boy. But what's this?
Sherlock grinned from under the hat, he knew what was coming next! Mycroft was going to be angry! The grin widened.
You don't know of the solar system? Any Ravenclaw would know that! You best fit the house of "SLYTHERIN!" The hat shouted out loud.
Sherlock almost skipped to the green clad table, almost. He was more dignified than that though. Mycroft was glaring from the Ravenclaw table and Sherlock shot him a happy smirk. 'Take that! For Redbeard!' Sherlock thought.