Question: The father of the regicide and also nephew of King Al Faisal was the twelfth son to who?

Context paragraphs:
Reem Al Faisal: Princess Reem al Faisal Al Saud (born in Jeddah) is a Saudi Arabian photographer, political journalist, and gallery owner, who lives in Jeddah and Paris.

2005 AFC Champions League: The 2005 AFC Champions League was the 24th edition of the top-level Asian club football tournament and the 3rd edition under the current AFC Champions League title.  The championship was retained by the Saudi Arabian club Al-Ittihad with a 5-3 aggregate victory over UAE side Al Ain.  Following a 1-1 draw at the Tahnon Bin Mohammed Stadium in Al Ain in the first leg, Al-Ittihad recorded a 4-2 victory at the Prince Abdullah Al Faisal Stadium in Jeddah to lift the trophy for the second consecutive season.  They also qualified for the 2005 FIFA Club World Cup.

Haifa bint Faisal: Haifa bint Faisal bin Abdulaziz Al Saud, also called Haifa Al Faisal, (Arabic: هيفاء بنت فيصل‎ ‎ ) (born 1950) is a member of the House of Saud.

Painting and Patronage: Painting & Patronage is a cultural and artistic exchange programme between Saudi Arabia and the international community.  It was founded in 1999 by Prince Khalid Al Faisal, son of the late King Faisal bin Abdul Aziz.

Saud bin Faisal bin Abdulaziz Al Saud: Saud bin Faisal bin Abdulaziz Al Saud (Arabic: سعود بن فيصل بن عبد العزيز آل سعود‎ ‎ ), also known as Saud Al Faisal (Arabic: سعود الفيصل‎ ‎ ‎; 2 January 1940 – 9 July 2015), was a Saudi diplomat and statesman who served as Saudi Arabia's foreign minister from 1975 to 2015.  A member of the Saudi royal family, he was the longest-serving foreign minister in world history since Klemens von Metternich.

Faisal bin Turki Al Faisal Al Saud: Faisal bin Turki Al Faisal Al Saud (born 27 March 1975), titled Prince Faisal bin Turki Al Faisal Al Saud, most commonly referenced as Faisal bin Turki.  He is the eldest son of Prince Turki bin Faisal Al Saud and brother of Red Bull athlete Prince Abdulaziz.  He is a member of the House of Saud, the Saudi Arabia royal family.  Similar to his father, Prince Faisal bin Turki studied International Relations at the Edmund A. Walsh School of Foreign Service at Georgetown University.  Faisal also studied at Calvin College, American Intercontinental University and the London School of Economics and Political Science, obtaining an MSc in Environmental Policy Planning and Regulation.

Faisal bin Musaid: Faisal bin Musaid bin Abdulaziz Al Saud (4 April 194418 June 1975) (Arabic: الأمير فيصل بن مساعد بن عبد العزيز آل سعود‎ ‎ , "ِ Fayṣal bin Musāʿid bin ʿAbd al-ʿAzīz ʾĀl Saʿūd ") was the regicide and also nephew of King Al Faisal.

George Cambridge, 2nd Marquess of Cambridge: George Francis Hugh Cambridge, 2nd Marquess of Cambridge, {'1': ", '2': ", '3': ", '4': "} (11 October 1895 – 16 April 1981), known as Prince George of Teck until 1917 and as Earl of Eltham from 1917 to 1927, was a minor member of the British Royal Family, a great-great-grandson of King George III and nephew of Queen Mary, the consort of King George V.  He was also nephew to the 1st Earl of Athlone.  He was the elder son of the 1st Marquess of Cambridge, formerly the Duke of Teck, and his wife, the former Lady Margaret Grosvenor.

Musa'id bin Abdulaziz Al Saud: Musa'id bin Abdulaziz Al Saud (1923 – 19 August 2013) was a member of the House of Saud.  He was the twelfth son of King Abdulaziz, the founder of Saudi Arabia.  He was the father of Faisal bin Musaid who was the assassin of his brother King Faisal.

Al Faisaliah Group: The Al Faisaliah Group (Arabic: مجموعة الفيصلية‎ ‎ ), is a Saudi-based conglomerate established in 1970.  Its name is derived from the name of founder, Abdullah Al Faisal, eldest son of the late King Faisal.

Supporting paragraphs: Musa'id bin Abdulaziz Al Saud Faisal bin Musaid
Answer: King Abdulaziz