The Scofield Bible Commentary, by Cyrus Ingerson Scofield, , at sacred-texts.com
Nebuchadnezzar was "father" of Belshazzar in the biblical sense that David is called "father" of Jesus, (Luk 1:32). Belshazzar was probably a grandson.
Or, grandfather. See note 2,
(See Scofield) - (Dan 5:2).
Darius the Median
The biblical order of the monarchs of Daniel's time, and of the period of the captivity and restoration of Judah, is as follows:
(1) Nebuchadnezzar (B.C. 604-561) with whom the captivity of Judah and the "times of the Gentiles"
(See Scofield) - (Luk 21:24).
(See Scofield) - (Rev 16:19),
began, and who established the first of the four world monarchies. (Dan 2:37); (Dan 2:38); (Dan 7:4).
(2) Belshazzar (prob B.C. 556), the Bel-shar-uzzar of the inscriptions, grandson of Nebuchadnezzar, and son of the victorious general Nabonidus. Belshazzar seems to have reigned as viceroy.
(3) Darius the Mede (Dan 5:31); (Dan 6:1-27); (Dan 9:1). Concerning this Darius secular history awaits further discoveries, as formerly in the case of Belshazzar. He has been conjectured to be identical with Gobryas, a Persian general. This Darius was "the son of Ahasuerus, of the seed of the Medes, which was made king over the realm of the Chaldeans" (Dan 9:1) "Ahasuerus," more a title than a name, the equivalent of the modern "Majesty," is used in Scripture of at least four personages, and is Persian rather than Median. That Darius the Mede was the "son" (or grandson) of an Ahasuerus proves no more than that he was, probably, through the seed of his mother, of the seed royal not only of Media, but also of Persia. There is but one Darius in Daniel.
See (Dan 9:1).)
(4) Cyrus, with whose rise to power came fully into existence the Medo-Persian, second of the world-empires (Dan 2:39); (Dan 7:5).
In Daniel's vision of this empire in "the third year of the reign of King Belshazzar" (Dan 8:1-4) the Median power of Darius is seen as the lesser of the two horns of the ram; the Persian power of Cyrus, under whom the Medo-Persian power was consolidated, as the "higher" horn which "came up last." Under Cyrus, who was prophetically named more than a century before his birth. (Isa 44:28-45); (Isa 44:4); the return to Palestine of the Jewish remnant began. (Ezr 1:1-4).
See (Dan 11:2); margin reference,
(See Scofield) - (Dan 11:2).