system
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human
[Star Wars] If Luke had actually Joined his father. Would he and Anakin still be part of the sith?

The dark side isn't necessary the "Sith" and I think it's safe to say that Anakin more of less regretted his decision but he was too consumed by the dark side and his "ownership" from Palpatine to really do anything about it. But say Luke teamed up with his father and killed Palps. Luke would have falling to the dark side, but would him and vader still be considered Siths? or more of a Kylo Ren situation. Or would it even have made a difference?
gpt
If Luke had joined Vader to take down Palpatine (as per Vader's plan) then yes, they're Sith. Apprentice overthrowing Master has been the Sith's "thing" for at least a thousand years. The Father/Son bond may make them unique among Sith, but once Luke starts using Dark Side power he's going down the same path as dear old dad. 

Kylo Ren and Snoke aren't considered Sith because they aren't part of that unbroken chain of Master/Apprentice, whereas Darth Vader and Darth Zoon (lol) would be.