Sherlock rolled his eyes slightly but smiled at John's teasing. Unusual, for him. But John made him smile. Sherlock liked John. He wanted to be his friend. But... They definitely wouldn't be in the same house. Sherlock didn't particularly want to be a Gryffindor or Hufflepuff or Ravenclaw so that left one option... Slytherin. And if John was in Gryffindor things wouldn't be too good. Everyone knew about the rivalry there.
"Just wanted to check on him, make sure he wasn't causing mischief yet," Greg replied to Mycroft with a smile and a shrug. Although what he had found was quite... Nice. Sherlock had been talking to someone and it hadn't been in a particularly nasty manner either. Greg had known Sherlock for a while, through Mycroft, and never had he seemed to have anything close to a friend.
"That's none of your business, Mycroft," Sherlock glared at his older brother. He knew Greg popping in was bad news and undoubtedly heralded the coming of Mycroft. Greg was like... Some kind of Mycroft magnet. Sherlock returned his gaze back to John. "Just ignore anything that my older brother says... He thinks he's very important and knows everything but he isn't and doesn't and nobody likes him very much."
"I like him, Sherlock," Greg sighed slightly, folding his arms.
"You don't count, Lestrade."