Leaders of the Progressive National Party, the De Facto governing party of the Hashemite Kingdom of Arabia since 1952* Leaders from the House of the People in bold, leaders from the House of Clergy and Tribes not in bold.
Note: The Socialists have little presence outside Damascus (and are a second-rate party within it). The Communists have little presence outside of Damascus University. The Islamic Party, traditionally the main opposition, have little presence outside of the old Saud stronghold of Riyadh and its surrounding area. Think as the government as being like the British system, except PMs can come from the Lords, which mainly consists of major religious and tribal leaders, and doesn't have many non-hereditary seats (note: when a Lord takes the PM job, he traditionally has his heir serve most day-to-day lordly duties in his stead). Note, the Kingdom includes modern day Iraq and Syria (minus the Kurdish parts), Jordan, Saudi, Kuwait, Qatar, Bahrain, the UAE, Yemen, Oman, Djibouti, Somalia, and Zanzibar. The Kingdom of Egypt and Sudan is their main ally in the region, and the Hashemites are very pro-Entente. The kings are the OTL Jordanian kings.
1952-7: Abdullah al-Selim al-Sabah
1957-67: Michel Aflaq
1967-71: Salah Jadid
1971-3: Hafez al-Assad
1973-80: Jamshid bin Abdullah
1980-5: Hafez al-Assad
1985-92: Isa bin Salman al-Khalifa
1992-2009: Qaboos bin Said al-Said
2009-12: Patriarch Ignatius Aphrem II
2012-: Amal Alamuddin