Exactly what it says on the tin.

Maybe Resistance golden boy Ben Solo is desperate enough to try ANYTHING to seduce his wayward brother back to the light.

Maybe Kylo Ren knows just how to break their newest Resistance captive, even if that captive just happens to be his own twin.

Maybe the whole thing is just an elaborate metaphorical power struggle happening in Kylo's mind.

However you want to make it happen, I need desperate, sweaty, kinky Kylo/Ben twincest to be a thing.