A Question about two certain Bleach captains?

they are the only two soul reapers who can use dual Zanpakutō. Yomamoto said they were special because of that. They were also the first to graduate the academy under yamamoto. I think there Bankai's are unique but after the last episode of the manga I dunno if we'll get the oppertunity to see them. I hope we still do. I think they were friends all there life which is why they work well together.