Dragon Kings don't have a lot of power, compared to queens, and mostly just have their title. Known kings include King Gill, King Char, King Humpback, and King Darkstalker. They tend to have only as much power as the Queens allow them to, with Darkstalker being the exception as he rules the NightWings alone in the old NightWing Kingdom.
List of Current Kings
King Darkstalker of the NightWings
List of Historical Kings
King Gill of the SeaWings
King Char of the SandWings