^
Yeah, but neither of them were the main/primary/assigned users of the IXA system. In the series, both of them only got to use it when the main users (Otoya and Nago)...well...frankly...when they let them use it. In the movie, they were only able to use it because Otoya and Nago had been beat up/prevented from using it.
The IXA system was also unique in that all the people that used it were identified/considered to be "users" of the IXA system. None of them were considered to "be" nor were any of them identified as being "Kamen Rider IXA".
As for Kivala...she's from DCD, which as we all know...doesn't really count since the entire series is basically a huge AU story.