King Abdullah became the king of Saudi Arabia on 1 August 2005, following the death of his half-brother King Fahd. Abdullah, like Fahd, was one of the many sons of Ibn Saud, the founder of modern Saudi Arabia. (Abdullah's mother was Fahda, the eighth of Ibn Saud's 16 wives.) Abdullah held important political posts throughout most of his adult life; he became mayor of Mecca as a young man and in 1962 he was appointed commander of the National Guard, a post he was still holding when he became king. He also served as deputy defense minister and was name crown prince when Fahd took the throne in 1982. Where Fahd was sometimes criticized for being too fond of western-style luxuries, Abdullah is regarded as a devout Muslim and a charismatic leader. After King Fahd suffered a serious stroke in 1995, Abdullah became the de facto ruler of Saudi Arabia until claiming the throne a decade later.
Abdullah is the sixth king of Saudi Arabia, following Abdul Aziz (Ibn Saud, 1932-53), Saud (1953-64), Faisal (1964-75), Khalid (1975-82), and Fahd (1982-2005)... Upon taking the throne in 2005, Abdullah name another half-brother, Prince Sultan, as the crown prince... According to a 2001 report in The Christian Science Monitor, Abdullah "has four wives, seven sons, and 15 daughters"... Some sources list his birth year as 1923; according to a 2005 story on CNN.com, "The exact date is unknown because no exact records of births or deaths were kept at the time in what was then an impoverished desert land."
Abdullah has the reputation of leading a relatively simple, pious life, in keeping with the kingdom's conservative Wahhabi philosophy. Some others in the royal family have been accused of lavish excesses. Abdullah is an ardent equestrian and founder of the Riyadh Equestrian Club. Pan-Arab in his outlook, Abdullah enjoys excellent relations with Syrian President Bashar al-Assad. Abdullah's Syrian-born wife is an Alawite, the religious sect to which Bashar belongs.
Since 1962, Abdullah has commanded the 57,000-member national guard, turning it into a modern army capable of defending the country's oil fields. He is also head of the Higher Economic Council and chair of the 18-member family council he formed in June 2000. Since he has no other full brothers, Abdullah has often found it difficult to create alliances within the enormous royal family. His son, Prince Mutib, is deputy commander of the national guard.

Source: wikipedia.org