He lost the one dearest to him by his mere existance. He lost his childhood in a childish hope of gaining his prize back. And he lost his remaining, other prize for a stranger.
This is a tale of Fëanor's childhood up to his rebirth and reunion with his family. There might be some time skipped between one event and the next, however. This story is included in my Seedlings universe, but it will only matter in later chapters; and so, I consider this an AU although the first chapters are true to the canon.