In addition to Nabunaid II, Belshazzar seems to have had another brother named Nebuchadnezzar, since the two Babylonian rebels against Darius Hystaspis both assumed the name of Nebuchadnezzar the son of Nabunaid (see the Behistun Inscription, I, 85, 89, 95). He had a sister also named Ina-esagilaremat, and a second named probably Ukabu'shai'-na.
Belshazzar had his own house in Babylon, where he seems to have been engaged in the woolen or clothing trade. He owned also estates from which he made large gifts to the gods. His father joins his name with his own in some of his prayers to the gods, and apparently appointed him commander of the army of Accad, whose especial duty it was to defend the city of Babylon against the attacks of the armies of Media and Persia.
It would appear from the Nabunaid-Cyrus Chronicle, that Belshazzar was de facto king of the Babylonian empire, all that was left of it, from the 4th to the 8th month of the 17th year of the reign of his father Nabunaid, and that he died on the night in which Babylon was taken by Gobryas of Gutium (that is, probably, DARIUS THE MEDE (which see)).
The objection to the historical character of the narrative of Daniel, based upon the fact that Belshazzar in , is said to have been the son of Nebuchadnezzar whereas the monuments state that he was the son of Nabunaid, is fully met by supposing that one of them was his real and the other his adoptive father; or by supposing that the queen-mother and Daniel referred to the greatest of his predecessors as his father, just as Omri is called by the Assyrians the father of Jehu, and as the claimants to the Medo-Pers throne are called on the Behistun Inscription the sons of Cyaxares, and as at present the reigning sheikhs of northern Arabia are all called the sons of Rashid, although in reality they are not his sons.
Literature
The best sources of information as to the life and times of Belshazzar for English readers are: The Records of the Past; Pinches, The Old Testament in the Light of the Historical Records of Assyria and Babylonia; Sayce, The Higher Criticism and the Monuments; and W. W. Wright's two great works, Daniel and His Prophecies and Daniel and His Critics.