In Guardians of the Galaxy, Vol 2,
Ego says that, of all his children, Peter Quill is the only one whose DNA enabled him to have Celestial powers.
Since Ego is a planet, his intrinsic DNA is diverse and fragmented towards tasks specific to each organism on the planet, though some of those organisms may have Celestial powers.
What is known about the unique aspects of a Celestial's DNA? Since Ego is the first Celestial that I recall after watching every Marvel movie, I wonder if the answer may have to come from the comics.