According to an answer to this question, Kylo Ren is not a true Sith.
As we saw in the end of episode VI
Palpatine and Vader are both killed.
Does this mean there are no longer any Sith in the galaxy? If there are no current Sith alive, how would the Sith come back?
Clearly there are followers of the dark side, but I get a bit confused on what the true difference is and why Kylo Ren could not simply re-start the Sith and claim to be one unless there was someone to dispute that claim.