Who were the first Olympian gods?

The gods and goddesses called Olympian refer to:

Zeus, Poseidon, Hestia, Hera, and Demeter: born after these by Zeus and Hera include Ares, Hephaestus, and Zeus's own children Athena, Artemis, Apollo, Dionysus, Hermes.

Some sources give Aphrodite the claim of being a daughter of Zeus, or a daughter born from the sea foam blood of Ouranus after his castration.