We knew that Peter Quill’s father was somebody from outer space, but now we know that the specific spaceman was Ego, the Living Planet, played by Kurt Russell.
It’s a significant departure from the answer in the comics, though clearly, the reasons for the change were all based on the rest of the story.
Technically, this question was answered prior to the movie itself, as the reveal was in the trailers, but it was still a big question that we had after the first movie that officially saw its answer in the sequel.