Arrow finally reveals season 7's new Green Arrow - and it's someone who's much closer to Oliver Queen that viewers may realize. Since Oliver Queen has been imprisoned for most of Arrow season 7 so far, and only recently got out in order to make sure he's ready to face whatever comes next in the Arrowverse's 2018 crossover event, Elseworlds, another Green Arrow has been helping keep Star City and its citizens safe in the interim. But, that's led to more questions than it has answers.
Throughout Arrow season 7, the mystery of who the new Green Arrow was has split the remaining members of Team Arrow, as some of them believed one of other Team Arrow members was taking up Oliver's mantle in secret - but that didn't turn out to be the case. Then it was believed that Oliver's son, William Queen, returned from the future and followed in his father's footsteps as the Green Arrow, which made sense considering that Arrow season 7's flashforwards are hinting at a dystopian future. However, it turns out that the new Green Arrow's real identity is something not many people expected, but is nevertheless an exciting twist.
In Arrow season 7 episode 8, "Unmasked," it's revealed that the new Green Arrow is Emiko Queen (played by Sea Shimooka on Arrow), Oliver Queen's half-sister from the comics. While her name isn't explicitly mentioned, it's clear who she is, and that is evidenced by Arrow season 7's midseason premiere originally being titled "My Name is Emiko Queen," before ultimately being changed to "Shattered Lives" after the first title leaked online.
Considering where "Unmasked" left off, it's safe to assume that Emiko Queen is Robert Queen's daughter, and is therefore still Oliver's half-sister. For those that are unaware, in the comics, Emiko Queen is the daughter of Robert Queen and Shado, though since there's no indication that Shado is her mother in the Arrowverse, it's possible that she may have an entirely different mother, which may be revealed when Arrow returns in 2019.
Furthermore, in the comics, the character Komodo was Emiko's guardian (which is why she was well-trained in archery), so it's possible that the only reason she's appearing in the Arrowverse now (and as the new Green Arrow) is because she's finally discovered who her real parents are, which is what led to her assuming her brother's superhero identity while he was in prison. With Elseworlds now taking over Arrow's final episode of 2018, any question about the new Green Arrow's identity will have to wait until next year.