This mythical Trojan prince was so handsome that he bewitched Eos, the goddess of dawn. She successfully petitioned Zeus to grant Tithonus immortality so she could be with him forever.
But Zeus interpreted her request literally. Tithonus didn’t die, but he did age. He lost his good looks and his faculties, and Eos lost her interest. She eventually shut him away in a room where he babbles endlessly.
It’s just a story. But as is often the case, truth turns out to be stranger than fiction. Plenty of species really are technically immortal. And unlike Tithonus, many are eternally youthful to boot.