Hide and Seek
John and Sherlock aren't a couple, by any means aside from business and paying for the rent. Sherlock comes back from a routine check up with the network that turns out to be not-so-routine. He's adopted a boy out of the underground lifestyle he'd been forced into, and both flat mates are innately drawn into becoming a brilliant family of three, until someone finds out he's not Sherlock's main interest anymore.