If I remember correctly, estio is the offspring of the black dragon. The dragon for some reason, maybe it was an accident but the egg fell to earth and crashed near tye village where he was raised. His "father" thinking it was gold, fought off the wolf that was guarding it (it turned out to be a guardian for estimate since he's technically a dragon) and brought the "gold" home. But when he arrived home, he found our mc. The only difference is that his eyes were originally gold but they changed to blend in with his surroundings.