we meet Mycroft Holmes, Sherlock's smarter older brother

Ah yes, I'd forgotten that, FF! It's a brilliant touch, and quite unexpected. You're waiting for Mycroft to slip up, thus proving Sherlock the real star of the show, but it does not happen.

It's another example of how Conan Doyle gives Sherlock just enough human foibles and frailties to make him engaging and likeable.