The term families is probably used here to signify the widespread empire of Nebuchadnezzar.
My servant - This title, so remarkable in the Old Testament as the especial epithet, first of Moses, and then of the Messiah, is thrice given to Nebuchadnezzar, and marks the greatness of the commission entrusted to him.
9 Behold, I will send and take all the families of the north, saith the LORD, and Nebuchadrezzar the king of Babylon, my servant, and will bring them against this land, and against the inhabitants thereof, and against all these nations round about, and will utterly destroy them, and make them an astonishment, and an hissing, and perpetual desolations.