King Abdullah chose Prince Meshal bin Abdul Aziz al-Saud to lead the 35-member committee, set up to ensure a smooth transition of power in the world's biggest oil producer, ruled by the al-Saud dynasty for 75 years.
The move is unlikely to have immediate consequences for the balance of power in the oil-rich kingdom, as Abdullah's successor Crown Prince Sultan, who will be 80 next month, is exempt from the new rules.
The king, who is in his early 80s, announced the appointment of his half- brother at a gathering of royal family members in Riyadh on Sunday evening, SPA said.
He said in a speech that the dynasty's founder Abdul Aziz bin Saud had advised his family to act as "one hand and one heart" and to "discuss any differences between us in a transparent manner and not allow anyone to interfere in our private matters."
A royal decree issued in October last year stated the committee's members must be the sons or grandsons of Saudi Arabia's founder, who died in 1953.
When King Fahd died in August 2005, then crown prince Abdullah was swiftly approved as the new monarch having already served as the kingdom's de facto ruler for some years because of Fahd's declining health.
The transfer of power in Saudi Arabia is keenly watched by oil markets as the vast desert nation sits on one quarter of the world's known oil reserves.
King Abdullah had a medical history even before he ascended to the throne in 2005.
Güncelleme Tarihi: 10 Aralık 2007, 16:23