Succession to the Saudi Arabian throne
The order of succession to the Saudi Arabian throne is determined by, and within, the House of Saud. Every King of Saudi Arabia, upon his death, has been succeeded by the crown prince, with a new crown prince then being appointed according to a loose form of agnatic seniority among the sons of Ibn Saud, though various members of the family have been bypassed for various reasons.
Source: Wikipedia — Succession to the Saudi Arabian throne (CC BY-SA 4.0)