The full history of Hephaestion's lineage is unknown, however, Jeanne Reames has suggested in that he descends from Athenian expatriates to Macedon. The most popular piece of evidence pointing to such a connection is in name-tracing. "Hephaestion" is the name of a temple on the Athenian acropolis, a name which hardly appears at all in Macedon at this time period. The date of Hephaestion's birth is also unknown, but it has been assumed that he was of a similar age as Alexander. When the two men first met is not certain, however, it is likely that Hephaestion shared Alexander's education in the village of Mieza with Aristotle as teacher, like other noble boys. Aristotle is known to have dedicated a volume of letters to him, but these are now lost. The philosopher Xenocrates also corresponded with Hephaestion.
Career and Relationships
Hephaestion accompanied Alexander's campaign in Asia from the very beginning, fighting in the Companion Cavalry Unit. Robin Lane Fox has referred to Hephaestion as Alexander's alter ego. A favorite story holds that while passing through the city of Troy, Alexander honoured the sacred tomb of the hero Achilles and Hephaestion that of Achilles' friend, Patroclus, assuming before the whole army the nature of the relation they shared.
After the Battle of Issus, Alexander and Hephaestion went to inspect the spoils of war, which included Darius' baggage train, family and royal harem. At this interval Sisygambis, the Persian queen mother, allegedly mistook the taller Hephaestion for Alexander, who graciously excused her by with the affirmation that "he too is Alexander". The rhetoric of the phrase has caused its authenticity to be called into question. Alexander's name, after all, translates literally to "protector of man", and so this may or may not have been a literary pun on Arrian's part. Nevertheless, the incident is still regarded as a prime example of the public emotional intimacy between the two men.
Hephaestion was not a particularly gifted battlefield commander, but excelled at logistics. Hephaestion was also often involved in city-planning and bridge-building. Whenever Alexander required Hephaestion's leadership on the battlefield, he usually placed another general with him, and sometimes Alexander himself, to make sure no mistakes were made.
Hephaestion may have been a gifted diplomat, as evidenced by his being repeatedly employed to negotiate with foreign leaders in India as well as with Persian aristocrats. Curtius calls Hephaestion "charming". The king which Hephaestion instated in Sidon enjoyed a popular reign. Hephaestion generally sided with Alexander concerning the adoption of Persian customs, specifically in the disastrous proskynesis affair.
After Philotas, son of Parmenion was implicated in an assassination attempt, he was tortured as part of interrogation by three men: Craterus, Hephaestion, and Parmenion's son-in-law Coenus. All three men subsequently rose in power. This incident also brought to power Erigyius of Mytilene, Perdiccas, and Leonnatus.
The Comapnion Cavalry unit, formerly under Philotas' command, was divided between Hephaestion and Cleitus the Black. The unit was then further divided into hipparchies, and as Hephaestion was a lesser commander than Cleitus, he maintained only one.
Before the India invasion and the crossing of the Hindu Kush mountains, in modern Afghanistan, Alexander made Hephaestion chiliarch, recognizing him as second in command. The responsibilities of the chiliarch put Hephaestion into opposition with Eumenes, the royal secretary.
During the India campaign Hephaestion again assumed military responsibilities in the vanguard, bridging rivers and leading one Companion squadron in the Battle of the Hydaspes River.
During the latter years of the campaign, Hephaestion's greatest rival for power was the general Craterus. The two men came near to blows in India, and had to be separated. Craterus was eventually dispatched with a bulk of the army returning to Macedon to replace Antipater as regent, while Hephaestion remained in Persia under Alexander's watch.
Following the march through the Gedrosian desert, Hephaestion and others were awarded gold crowns (possibly for bravery). By this point, Hephaestion had become a somatophylax.
Shortly before Hephaestion's death, he and Eumenes quarrelled - specifically over the housing of a flute-player. Following Hephaestion's death, Eumenes was one of the first to dedicate arms to the dead man.
Death and Funeral
In the autumn of 324 BC, Alexander's army was stationed in the city of Ecbatana (today called Hamadan) for the winter. Hephaestion fell sick during the games that were being held for the court and died a week later. Described symptoms are compatible with typhoid fever, but the possibility of poisoning was never ruled out. Hephaestion's death deeply affected Alexander, but the extent to which the king fell out of bounds with grief has been disputed.
Reportedly, Alexander responded to the death by shaving his head, cropping the manes of the army horses, cancelling all the festivities, and crucifying the attending doctor. He set out immediately for Babylon with the body, where fabulous funeral games were held. The oracle at Sidon, after being petitioned by Alexander for the correct way to honor Hephaestion, conferred divine hero status upon the dead man.
Many have found cause to link the deaths of Alexander and Hephaestion, especially as Alexander died within eight months following Hephaestion's demise.
The funeral pyre in Babylon that Alexander built Hephaestion cost 10,000 talents  of Persian gold. As Plutarch says,
- "...at Ecbatana there fell upon Alexander a stunning blow, the loss of Hephaestion. His intimate boyhood love, Hephaestion was gone, the congenial enthusiastic nature which had been so much more to Alexander than Ptolemy's sagacity or Nearchus' careful courage, the friend, more than a friend, and closer than a brother, who alone awoke a gentler emotion in the breast of the lonely Conqueror....
- For there come, alike in discouragement and exaltation, to all men, however strong of body or brain, moments of craving, in which the soul gropes blindly for another soul; and the most strong, if he owns this need most rarely, feels it most imperious.''
- Arrian. The Campaigns of Alexander. Trans. Aubrey de Selincourt. London: Penguin Books Ltd. 1958.
- Plutarch. Life of Alexander. 
- Fox, Robin Lane. Alexander the Great. 1973. Rpt. London: Penguin Books Ltd. 2004.
- Reames-Zimmerman, Jeanne. Hephaistion Amyntoros: Eminence Grise at the Court of Alexander the Great. Diss. The Pennsylvania State University, c1998. (abstract)
- Borza, Eugene and Jeanne Reames. Some New Thoughts on the Death of Alexander the Great, The Ancient World 31.1 (2000) 1-9.
- Bosworth, Albert Brian. Hephaistion. In: Simon Hornblower, Antony Spawforth (Hrsg.): The Oxford Classical Dictionary. 3. Aufl., Oxford University Press, Oxford 1996, ISBN 0-19-866172-X.
- Carney, Elizabeth D. Alexander the Great and the Macedonian Aristocracy. Dissertation, Duke University, 1975.
- Heckel, Waldemar. Hephaistion. In: Ders.: The Marshals of Alexander's Empire. Routledge, London 1992, ISBN 0-415-05053-7.
- Reames-Zimmerman, Jeanne. An Atypical Affair? Alexander the Great, Hephaistion, and the Nature of Their Relationship. In: The Ancient History Bulletin 13.3 (1999), S. 81–96.