Michael Burnham and Spock have a complicated relationship in Star Trek: Discovery, according to the show's lead actress, Sonequa Martin-Green. In Discovery, the human Burnham was orphaned at an early age due to a Klingon attack and subsequently adopted by Sarek and his wife Amanda, otherwise known as the parents of iconic Star Trek character, Spock. Burnham was raised alongside her new foster brother as a Vulcan and although Discovery's first season spent plenty of time exploring the dynamic between Burnham and Sarek, it only featured a few passing references to Spock.
That, however, is set to change in the show's forthcoming second season. Discovery season one dramatically ended with the long-awaited appearance of the good ship Enterprise, thus bringing with it a host of recognizable characters such as Christopher Pike (played by Anson Mount) and, more significantly for Burnham, Spock (Ethan Peck). While little is currently known about how Spock's presence will tie into Discovery's second season, the first-look trailer suggested that the Vulcan would be in some kind of peril and Burnham would take it upon herself to come to her foster brother's aid.
In an interview with IGN, Burnham actress, Sonequa Martin-Green, spoke about what adventures await her character in Discovery season 2 and what the addition of Spock to the show's cast could mean for the newly re-instated Starfleet officer. Martin-Green stated:
"I will say... that it is not a simple relationship [between Spock and Burnham]. It is a very complicated relationship. It's a highly emotional relationship. And it will take some work."
The actress also spoke a little on the mysterious 'Red Angel' seen in the trailer for Discovery season 2, confirming that the strange phenomenon is something that connects Burnham and Spock:
"The Red Angel appears to Michael Burnham at a very, very critical moment. And then what I find out later is that Spock has also seen this same Red Angel, but when he was a child."
Given both the inherent complexity of Vulcan/human relationships and the unique bond between Burnham and Sarek, it perhaps shouldn't come as a great surprise that the two foster siblings would also have an emotional and layered relationship. It's also worth remembering that in the episode "Lethe," Sarek was revealed to have picked Spock over Burnham for a highly coveted spot in the Vulcan Expeditionary Group - an offer Spock ultimately rejected in favor of joining Starfleet. With Burnham now aware of this fact and Sarek very annoyed indeed about his son's career choice, it might be expected that some jealousy or animosity would exist between Spock and his sister, but those feelings aren't particularly Vulcan things to experience.
As such, viewers can perhaps expect a resurgence of Spock's human and Vulcan struggle in Discovery season 2, a story arc that has been an ever-present trait of the character. However, this inner conflict will surely take on an entirely new dimension now it has been established that Spock has a human foster sister.
Star Trek: Discovery season 2 is set to premiere January 17th 2019 on CBS All Access.