At first he thought it was a joke, when Sherlock said his twin would be moving in... It wasn't.

He wasn't sure how to feel about it, he had dealt enough with Sherlock's siblings to know they weren't precisely someone you'd enjoy having around. Sherlock had also never mentioned having a twin before, in fact, not even Mycroft had said anything about it... But still, here they were, staying over in 221B baker street