Darth Nihilus's leader ability
... his leader ability does not seem to affect Kylo Ren although he appears to be a Sith because he's wielding a red lightsaber. As noted by looking at what category Kylo Ren falls in, I don't see him...
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Being a dark side force user doesn't make you a Sith. Sith is a specific faction or organisation. All we know for now is that he is part of the faction called Knights of Ren. Once others of the knights are known then Kylo will probably get that tag.
