Daniel 5:10

Now the queen... came into the banquet house.

The wives and concubines were already there, but the queen only came on account of hearing of the awful portent. This convinces us that the queen was not the wife of Belshazzar at all, but his mother and the wife of king Nabonedus, his father, who was besieged at Borsippa. This accounts for her familiarity with the character of Daniel, of whom Belshazzar seemed to have no knowledge. Daniel was now an old man; during the long reign of Nebuchadnezzar he had been. prominent figure, but under such frivolous princes as his successors Daniel had fallen into obscurity.