Which Greek deity was the firstborn of Cronus (also known as Kronos), the Titan who ate his children whole?

The Titans Cronus and Rhea famously had six children, which included Zeus, Hera, Demeter, Poseidon, Hades, and Hestia.

However, Cronus was told in a prophecy that he would be overthrown by one of his children (much like he overthrew his own father)

In an attempt to prevent this fate, Cronus decided to devour his children whole the moment they were born.

It is well known that Zeus then fulfilled that prophecy when his mother Rhea decided to feed Cronus a rock disguised as Zeus instead of the real baby. This allowed Zeus to grow up and eventually free the rest of his siblings from inside Cronus.

However, this means that Zeus was in fact the youngest of the six children birthed by Rhea. The eldest is perhaps the least well-known in modern times, the goddess Hestia, who is the goddess of the home and the hearth, followed by Demeter, Hera, Hades, Poseidon, and then finally, Zeus.