Original: Ares, Hermes, Hephaestus, Aphrodite, Athena, Apollo, Artemis, the Charites, Heracles, Dionysus, Hebe, and Persephone were children of Zeus.
Simplified: Zeus, Hera, Poseidon, Ares, Hermes, Hephaestus, Aphrodite, Athena, Apollo, and Artemis are always considered to be Olympians. Hebe, Helios, Hestia, Demeter, Dionysus, Hades, and Persephone are the gods who have sometimes been Olympians.