He was born the son of Philip II of Macedon, and Princess Olympia, daughter of King Neoptolemus of Epirus. As a youth his teacher was Aristotle, and Alexander's empire is one of the primary reasons why European culture is based largely on Greek civilization. When he was about 25 he was adopted by Ada, widow and sister of Satrap Idrieus (one source says that it was Alexander who adopted Ada, as his mother), and he appointed her satrap of Caria.
He was also the foster-brother of Clitus Niger (see Roman Empire), according to some sources.