The Saud clan, which had ruled part of the Arabian peninsula, was expelled from the emirate of Nejd in the 19th century by the rival Rashid dynasty. In 1902, a member of the Saud family, Abdul Aziz (called Ibn Saud), and his small band of supporters captured Nejd's capital, Riyadh. He went on to conquer central Arabia, and in 1932 his domains officially became the Kingdom of Saudi Arabia.

Ibn Saud died in 1952 and was succeeded by his son Saud. King Saud was deposed by his family in 1964 and replaced by another of Ibn Saud's sons, Faisal. King Faisal did much to moderize Saudi Arabia and was respected around the world, but in 1975 he was assassinated by a disgruntled relative. The next two kings, Khalid and Fahd, were also sons of Ibn Saud. ... The royal family has thousands of members and controls the country's government.

from Royalty in Saudi Arabia