There are two Niobes in Greek Myth: one was the daughter of Tantalus, and a prideful mother whose children were slain by Apollo and Artemis. The other, less well-known, was the daughter of Phorenus, and the mother, by Zeus of Argus – for whom the city of Argos was named.
It should be noted also, that thus Argus was not any of the other figures in Greek Myth named either Argos or Argus – he was not the shipwright who built the Argo, nor the son of Jason and Medea named for that shipwright. Neither was he a legendarily faithful dog whose master was Odysseus, nor the hundred-eyed giant known as Argus Panoptes. He was just this guy, who happened to be the third king of Argos, and the first child Zeus had by a mortal woman. He would have lots of half-siblings, mostly posthumously.