Question: What is the name of the paternal grandfather of Alexander Macmillan ?

Context paragraphs:
Maurice Macmillan: Maurice Victor Macmillan, Viscount Macmillan of Ovenden PC (27 January 1921 – 10 March 1984) was a British Conservative Party politician and Member of Parliament.  He was the only son of Harold Macmillan, who previously served as Prime Minister of the United Kingdom.

Gordon Holmes Alexander MacMillan: General Sir Gordon Holmes Alexander MacMillan of MacMillan and Knap, (7 January 1897 – 21 January 1986) was a professional soldier who rose to become a general in the British Army.  As a young officer during the First World War, he displayed outstanding bravery and was awarded a Military Cross and two Bars.  At the age of 19 and while still a second lieutenant, he was appointed acting adjutant of the 2nd Battalion, Argyll and Sutherland Highlanders.  Between the World Wars, MacMillan remained in the army, occupying posts of increasing seniority.  He married Marian Blakiston Houston in 1929, and they had one daughter and four sons.

Claudia Capitolina: Claudia Capitolina (Greek: η Κλαuδία Καπιτωλίνα ) was an Egyptian Greek woman who lived in the Roman Empire, in the 1st century and possibly in the 2nd century.  Capitolina came from a distinguished family of Equestrian rank.  She was born and raised in Alexandria, Egypt.  Capitolina was the daughter and only child of Tiberius Claudius Balbilus by his unnamed wife.  The cognomen "Capitolina", is probably from her maternal side.  Her father was one of the highest magistrates of Equestrian rank that served in Rome.  Balbilus was an astrologer and a learned scholar, who was later Prefect of Egypt.  Capitolina’s paternal grandfather, was an Egyptian Greek Grammarian and Astrologer called Thrasyllus of Mendes or Tiberius Claudius Thrasyllus, who was a friend of the Roman Emperor Tiberius, while her paternal grandmother was Greek Princess Aka II of Commagene, who was a great, granddaughter of King Antiochus I Theos of Commagene.  Her paternal cousin was Ennia Thrasylla who married the Praetorian prefect of the Praetorian Guard, Naevius Sutorius Macro.

St. Nerses I: Nerses I the Great (Armenian: Սուրբ Ներսես Ա.  Մեծ ) was an Armenian Catholicos (or Patriarch) who lived in the fourth century.  He was the son of At'anagenes and his mother was the Arsacid Princess Bambish, a sister of King Tigranes VII (Tiran) and a daughter of King Khosrov III.  His paternal grandfather was St. Husik I whose paternal grandfather was Saint Gregory the Illuminator.

Daniel Macmillan, Viscount Macmillan of Ovenden: Daniel Maurice Alan Macmillan, Viscount Macmillan of Ovenden (born 9 October 1974) is a British fashion designer and the only son of Alexander Macmillan, 2nd Earl of Stockton.  As the heir apparent to an earldom, he uses his father's secondary title of Viscount Macmillan of Ovenden as a courtesy title.  He is a great-grandson of the former Prime Minister Harold Macmillan, 1st Earl of Stockton.

Marcia Servilia Sorana: Marcia Servilia Sorana or commonly known as Servilia (40s-66) was the daughter of Roman Senator Quintus Marcius Barea Soranus and her mother may have been from the gens Servilia.  Servilia's paternal uncle was the Roman Senator Quintus Marcius Barea Sura, who was a friend to the future Roman Emperor Vespasian.  Her paternal cousins were Marcia (mother of Ulpia Marciana and of future Roman Emperor Trajan) and Marcia Furnilla (the second wife of the future Roman Emperor Titus).  Her paternal grandfather Quintus Marcius Barea Soranus was Suffect Consul in 34 and twice Proconsul of Africa.

Alexander Macmillan, 2nd Earl of Stockton: Alexander Daniel Alan Macmillan, 2nd Earl of Stockton (born 10 October 1943) is a Conservative Party politician in the United Kingdom.  He is the first son of the late Conservative politician Maurice Macmillan and the first grandson of former prime minister Harold Macmillan.

Johann Georg Hiedler: Johann Georg Hitler (baptised 28 February 1792 – 9 February 1857) was considered the officially accepted paternal grandfather of Adolf Hitler by the Third Reich.  Whether Johann Georg was in fact Hitler's biological paternal grandfather is disputed by modern historians.

Alexander MacMillan (publisher): Alexander MacMillan (Scottish Gaelic: "Alasdair MacMhaolain" ; 3 October 1818 – 26 January 1896), born in Irvine, Ayrshire, Scotland, was a cofounder, in 1843, with his brother Daniel of Macmillan Publishers.  His family were crofters from the Isle of Arran.

Macmillan's Magazine: Macmillan's Magazine was a monthly British magazine from 1859 to 1907 published by Alexander Macmillan.

Supporting paragraphs: Alexander Macmillan, 2nd Earl of Stockton Maurice Macmillan
Answer: Harold Macmillan