The Zaydi imam always came from the social group known as sayyids, or descendants of the Prophet Muhammad. The sayyids had been an elite group of the Yemeni highlands since the foundation of the imamate in the ninth century. However, the extent of their power fluctuated over time, and their domination was only possible with the support of other local groups.

Sayyids were not unique to northern Yemen. They played an essential role in other regions of Yemen (for example, in Hadramawt) and other parts of the Muslim world, but it was only in the Yemeni highlands that they succeeded in holding political power for several centuries.