Who is the father of Star-Lord?

Star-Lord's father is Ego, the Living Planet. In the MCU, Ego is a powerful Celestial who takes human form and reveals that he is Peter Quill's biological father in Guardians of the Galaxy Vol. 2.

Ego explains that he planted extensions of himself on planets across the universe and fathered children with different species in an attempt to produce offspring capable of helping him activate his expansion. Peter is valuable because he inherited Celestial energy from Ego. Ego's plan is to transform worlds throughout the universe into extensions of himself, destroying existing life in the process.

Peter's relationship with Ego is complicated by the murder of his human mother, Meredith Quill. After learning the truth, Peter rejects Ego's plan and helps the Guardians destroy him. Yondu is not Peter's biological father, but he abducted and raised him, making Yondu his adoptive father figure. Ronan and Thanos are major antagonists, not members of Peter's family.