Kira has not been shown since Gin betrayed Aizen. More importantly, as Gin never verbalized his motives (we the readers got a peek into his memories and thought process), it is unlikely that even Rangiku knows why he did what he did. Most likely, all Kira would find out is that Gin turned on Aizen at the end. However, both Kira and Rangiku are unlikely to have the faintest clue why Gin did anything, because Gin never shared.