Zagreus

Zagreus is the Olympian God of Rebirth and is the only Olympian Deity that is shown to be able to go through a Rebirth Cycle at least once, he has been the half-brother of both the famous Heracles and infamous Adolf Hitler within his two lifespans, the only bloodline of the Big Three that he has never belonged to is Poseidon's bloodline.

Brief First Life
Zagreus was originally born as the son of Zeus and Gaea before the last of the Titans were finally cast into Tartarus following the First Olympian War, both loved him and Zeus proclaimed Zagreus would be the Prince of the Heavens and Zeus's successor should Zeus ever be overthrown as Kronos had been, Hera was the least upset at this and instead was fueled with a jealous fury sought to remove the glitch that was Zagreus from her "perfect family".

Hera convinced the remaining Titans that killing Zagreus would be the perfect way in which to get back at Zeus for overthrowing their domains, Hera left the young baby Zagreus where the Titans could harm him and watched with glee as the Titans distracted him with toys, as they attempted to kill him Zagreus surprised them all by fleeing and fluidly shape-shifting into countless animals. Finally, he took the form of a bull, and in that form they caught him, tore him to pieces, and devoured him.

Horrified by the death and cannibalism of her favorite child by her own previously favored children, Gaea held the Titans fast as an enraged Zeus hurled a thunderbolt from his Master bolt at the Titans, turning them to ashes. From the bloody remains of the child, Gaea was able to retrieve his heart, the last of his divine essence.

Rebirth
Gaea orchestrated some time following the marriage of Hades and Persephone, before long Persephone became pregnant with Hades's first son and Gaea in the form of a kind Crone offered Persephone a Magical Tonic that would aid the Queen of the Underworld with her pregnancy,

Trivia

 * In actual Greek Myth, Zagreus's identity and fate is far more complicated. Commonly he is the son of Zeus and Persephone, or Hades and Persephone, in the former he was later reborn as Dionysus or Demeter resurrected him but was never mentioned again in the mythos.
 * The earliest records of Zagreus describe him in Quota: "Mistress Earth and Zagreus who art above all other gods". But a invocation linking him with the earth goddess Gaia and placing him above all other gods, could not fit easily into the Olympian religion of Zeus. Hence there was much confusion as to the myth behind Zagreus, and the true sources.
 * In Greek a hunter who catches living animals is called zagreus, Karl Kerenyi notes, and the Ionian word zagre signifies a "pit for the capture of live animals".