The Ten Tribes was a group made of ten smaller groups that governed the civilization of Capella IV.
In the late 23rd century, they were ruled by a single leader called a Teer. In 2267, the Teer of the Ten Tribes was Akaar.
Shortly after Kirk, Spock, and McCoy arrived that year to negotiate with Akaar, he was murdered in a coup, and succeeded by Maab. Maab's reign (and remaining life) were measured in days; he was betrayed by the same Klingon who had earlier urged him to power, and this resulted in his death.
The position of Teer was then occupied by the newborn son of Akaar, Leonard James Akaar, whose mother Eleen ruled as regent. (TOS: "Friday's Child")