[7] Though contemporary sources suggest an origin in southern Mesopotamia, such as the Uruk prophecy text describing Nabopolassar as a "king of the sea" (i.e. southernmost Babylonia) and a letter from the Assyrian king Sinsharishkun describing him as "of the lower sea" (also southernmost Babylonia), there is no source that ascribes him a specific ethnic origin.

In 2007, the Assyriologist Michael Jursa identified Nabopolassar as the son of Nebuchadnezzar (or Kudurru), a governor of Uruk who had been appointed by the Neo-Assyrian king Ashurbanipal.

Neriglissar was powerful and influential prior to becoming king, but was not related to the dynasty by blood, instead likely being of Aramean origin, probably of the Puqudu clan.

[16][7] He was not completely unconnected to the Chaldean dynasty, however, having secured his claim to the throne through marriage to one of Nebuchadnezzar II's daughters, possibly Kaššaya.

Why Labashi-Marduk was deposed is not known, but it is possible that he was the son of Neriglissar and a wife other than Nebuchadnezzar II's daughter, and thus completely unconnected to the Chaldean dynasty.

[22] Nabonidus's rise to the throne put Belshazzar first in the line of succession (it would not have been suitable for him to have become king himself while his father was still alive) and also made him one of the wealthiest men in Babylonia as he inherited Labashi-Marduk's family's estates.