Sherlock co-creator Mark Gatiss says Mycroft Holmes is even more intelligent than the detective himself.
References in the original Sherlock Holmes stories suggest Sherlock's brother does indeed possess superior powers of observation and deduction, although his sedentary nature prevents him from being an effective detective.
And Gatiss, who plays Mycroft in the series, says he'd like future episodes of the show to reveal more about the brothers' abrasive relationship and Mycroft's own talents.
"Why are the Holmes brothers the way they are? What are their parents like? Maybe we'll see one day. I'd like to find a way of showing more than we have that [Mycroft] is actually even cleverer than Sherlock," Gatiss said during a webchat with Sherlock's US broadcaster PBS.
But he admitted it could be a long time before viewers learn more about the brothers' enigmatic past.
"Far better to leave things in everyone's imaginations," said Gatiss in response to a fan question about whether the Holmes family background was to be explained in the new series. "It's nice to give little hints here and there but never a full answer."
Gatiss revealed that the problem of how much information to give the audience about Mycroft and Sherlock had arisen during the making of A Study in Pink, the opening episode of the 2010 reboot.
"We actually cut a bit from Pink which gave a bit too much away about the obvious frisson of animosity that exists between them," the actor and co-creator said, adding: "It's not there in the original stories. It comes entirely from Billy Wilder and Izzy Diamond's brilliant [1970 film] The Private Life of Sherlock Holmes and Christopher Lee's cold, disdainful Mycroft. If you haven't seen it - do!"
Gatiss also discussed how he came to play the part himself, confirming that his Mycroft has a real-life inspiration.
"Mycroft wasn't in the pilot, so no [I wasn't always planning to play him]. But when we came to rethinking and reshooting episode one it just sort of happened. I'd just auditioned to play Peter Mandelson in a TV film and we'd already discussed how reptilian and Mandelsonian we wanted Mycroft to be. We also saw a great chance to fool people into thinking I was Moriarty. And it worked!"