Five of his sons have ruled as absolute monarchs of the world's richest oil producer, while others members of the family hold many of the powerful offices of state.

In his 80s, the king remains an energetic player at home and abroad

Abdullah bin Abdul-Aziz became king of Saudi Arabia in August 2005, following the death of his chronically ill half-brother King Fahd who had withdrawn from public life in the mid-1990s.

He enjoys a reputation for honesty and being untainted by corruption and his philosophy has been to keep a balance between the simple traditions of Saudi life and the need for modernisation and reform.

The monarch also recognises the need for close political and economic ties with the West, but balanced by closer links with other Arab states.

Steps he has taken towards reform have been carefully measured, showing sensitivity to the wishes of opponents of change as well as advocates.

Abdullah was born in Riyadh in 1923 to the kingdom's founder, Abdul Aziz Ibn Saud, and a woman from the rival Rashid clan. He received a traditional Islamic education and grew up steeped in the traditions and customs of the ruling family.

His first public office was as mayor of the holy city of Mecca and in 1963, he became deputy defence minister and commander of the National Guard - Saudi Arabia's most reliable armed force - a post he has held ever since.

After becoming crown prince in 1982, he mediated in several inter-Arab disputes and he remains a strong critic of Israel's post-1967 occupation and of US support for Israel.

In March 2002, he proposed pan-Arab normalisation with Israel if it withdrew to its pre-1967 boundaries, a plan which now underpins the Arab position regarding Middle East peace.

King Abdullah is an imposing figure who acquired the charisma of an international statesman without adopting the flamboyance of some contemporaries. He normally talks quietly in colloquial Arabic and speaks with a stutter.

Prince Sultan has been defence minister since 1963

Crown Prince Sultan is one of the senior members of the ruling family who has generally favoured close ties with the United States - his son Bandar serving as Saudi ambassador in Washington for 22 years.

The crown prince is chairman of the Higher Council for Islamic Affairs which provides funds for Muslim communities around the world. He strongly denies accusations that Saudi money has been paid to charities with alleged links to terrorism.

He was born in Riyadh in 1928, one of the seven male offspring of Ibn Saud's favourite wife Hassa bint Ahmad al-Sudairi - the Sudairi seven, as they are known.

He made his first major appearance in 1947 when he was appointed governor of Riyadh. Prince Sultan has held his current post in the Ministry of Defence and Aviation since 1963.

In this capacity he has been closely involved in the development of the national airline, Saudia, and the construction of rail links.

He has also been closely involved in negotiating Saudi Arabia's massive arms purchases, including the al-Yamamah deals with the UK and BAE Systems, which are the focus of corruption allegations.

He was the founder, in 1986, of the Saudi National Commission for Wildlife Conservation.

Naif is the fifth member of the princely Sudairi Seven

Interior Minister Prince Naif has responsibility for maintaining security and law and order within the kingdom.

He is personally committed to maintaining Saudi Arabia's conservative traditions based on the Wahhabi doctrine of Islam and he is probably the least comfortable with the kind of modernising reforms advocated by King Abdullah.

He was born in Riyadh in 1934 and is another of the seven sons of Ibn Saud's favourite wife, Hassa bint Ahmad al-Sudairi.

In 1953 Prince Naif became governor of Riyadh, and shortly after that was made deputy minister of the interior. He was appointed minister of the interior in 1975.

In the aftermath of the 11 September 2001 attacks in the United States, perpetrated mostly by Saudi nationals, Prince Naif came under strong US criticism.

He was also accused of failing to take sufficient action to hunt down those responsible for bomb attacks on Western targets in Saudi Arabia. But when Saudis and other Arabs also became victims of such bombings, Prince Naif bowed to pressure from within the royal family to launch a hunt for Islamic militants.

Prince Saud heads the third generation of Saudi Arabian leaders

Foreign Minister Saud al-Faisal is the international face of Saudi Arabia. Son of King Faisal, he was born in 1940 and was among the first generation to receive both a traditional and a Western education.

He completed his studies in 1964 when he graduated with a BA in Economics from Princeton University in the United States. In 1970, Prince Saud became deputy governor of the former state-owned natural resources company, Petromin, and the following year was appointed deputy minister of petroleum and mineral resources.

However, his diplomatic bearing, knowledge of the West and his command of English made him a natural choice for the foreign ministry.

Prince Saud has played a leading role in his country's efforts to promote a peaceful solution to the Arab-Israeli conflict. He worked hard to win broad Arab support for then Crown Prince Abdullah's plan offering Israel peace and normal relations if it handed back occupied Arab land.

Since 11 September 2001, he has vigorously argued for a distinction to be made in Western minds between Islam and terrorism.

At the same time, he has emerged as one of the strongest supporters of political and social reform, arguing that this should be both gradual and inspired from within the kingdom, rather than imposed from outside.