Hestia, Demeter, Hera, Hades and Poseidon.
Cronus feared being overthrown by his offspring, hence he swallowed them at birth. However Zeus, his first born, was saved by his mother, and went on to overthrow him to become the Father of Gods and men.
Cronus is the father of Zeus. Cronus swallowed his own children. But Rhea saved Zeus and hid him from Cronus so he wouldn't swallow him. Rhea gave cronus a rock wrapped in cloth instead of Zeus so Cronus swallowed the rock.
Cronus
Cronus!
Quite possibly, as Cronus the father of Poseidon swallowed him shortly after birth.
Zeus, by Cronus.
because he swallowed his children
Cronus swallowed his children by Rhea, these being Hades, Hestia, Hera, Demeter, and Poseidon.
Poseidon was born to Cronus and the sister of Cronus he was swallowed by Cronus and was saved by his brother Zeus because Zeus made Cronus puke up all his brothers and sisters.
Demeter was a daughter of Cronus and Rhea. She was swallowed by Cronus and later vomited up because Zeus tricked Cronus into eating vomitus.
Cronus; and Zeus swallowed Metis and thus Athena was born of his head - Aura also swallowed her child.
He did not have one; as when he was born from Rhea he was swallowed by his father Cronus.