Alexander's lifelong companion was Hephaestion, the son of a Macedonian noble. Hephaestion also held the position of second-in-command of Alexander's forces until his death, which devastated Alexander. The full extent of his relationship with Hephaestion is the subject of much historical speculation.

Alexander married two women: Roxana, daughter of a Bactrian nobleman, Oxyartes, and Stateira, a Persian princess and daughter of Darius III of Persia. There is also an accepted tradition of a third wife- Parysatis whom he is supposed to have married in Persia though nothing is known about her. Another personage from the court of Darius III with whom he was intimate was the male eunuch Bagoas. His son by Roxana, Alexander IV of Macedon, was killed after the death of his father, before he reached adulthood.
Alexander was admired during his lifetime for treating all his lovers humanely

Successor
On his death bed, his marshals asked him to whom he bequeathed his kingdom. Since Alexander had no obvious and legitimate heir (his son Alexander IV would be born after his death, and his other son was by a concubine, not a wife), it was a question of vital importance. There is some debate to what Alexander replied. Some believe that Alexander said, "Kratisto" (that is, "To the strongest!") or "Krat'eroi" (to the stronger).

Alexander may have said, "Krater'oi" (to Craterus). This is possible because the Greek pronunciation of "the stronger" and "Craterus" differ only by the position of the accented syllable. Most scholars believe that if Alexander did intend to choose one of his generals, his obvious choice would have been Craterus because he was the commander of the largest part of the army (infantry), because he had proven himself to be an excellent strategist, and because he displayed traits of the "ideal" Macedonian. But Craterus was not around, and the others may have chosen to hear "Krat'eroi" — the stronger. Regardless of his reply, Craterus does not appear to have pressed the issue. The empire then split amongst his successors (the Diadochi).

Before long, accusations of foul play were being thrown about by his generals at one another, and no contemporaneous source can be fully trusted.