Question: why kylo ren not darth?
Answer: Kylo Ren is no "Darth" because he's no Sith. ... As it was previously revealed, the honorific in his name isn't "Darth" but "Ren" — as in the Knights of Ren, a previously unknown group in the Star Wars universe. "Kylo Ren is not a Sith," Abrams says in the interview.