The father-son relationship
It would be an understatement to describe this father-son relationship as strained.
Over the past few seasons, Sherlock has compared his dad to somebody who steals candy from children and clubs baby seals. He doesn't think his dad actually cares, and is doing only what he has to out of a sense of familial obligations.
When Morland made a dinner date with Sherlock and Dr. Joan Watson, Sherlock was convinced that his father wouldn’t show. When pressed by Joan, he described his father as a "serial absentee and a pathological maker and breaker of promises." The detective proved to be right when his father bailed on their plans yet again.
Sherlock has never felt in control of his own life, starting from when Morland sent him to boarding school as a young child. He still feels patronized, as Morland won't give the detective full control of his trust fund and pays for employees to keep tabs on him.
While the relationship may be difficult and complex, it's also part of what makes the story so relatable. "Everyone has a father or a mother somewhere along the line who affected their lives somehow," said Noble. "Really it’s this father-son or mother-daughter stuff which I think is universal, that all of us understand and it resonates with all of us."