It's always been a shame, a big wasted opportunity to reveal and develop both Xebec and Kaido's character, and Xebec and Kaido's relationship could have been a darker mirror to Roger and Shanks' relation.
Also Kaido did seem to have some genuine care and trust at least in and for King and Jack, yet his relationship with them was neglected and underdevelopped as hell save for a few scenes with King, and he didn't even had any real moment with Queen. At least how he met them and they joined his crew, and the origins of the Beast Pirates should have been part of his flashback.